feat(desktop): runtime-configurable backend server address

The desktop shell is one generic .deb/.AppImage distributed via
mca/public_releases, not built per-booth, but the backend origin was baked
in at build time (VITE_API_BASE, hardcoded to http://127.0.0.1:3000) — the
same installer could never point at a different appliance without a
rebuild.

Adds ConnectScreen (shown before Login in Tauri when no backend is saved),
backed by tauri-plugin-store persisting the operator-entered URL across
restarts. CSP's connect-src tightens to 'self' only — all backend traffic
already routes through tauri-plugin-http/websocket, which run Rust-side
and are outside connect-src's reach anyway — and the real access boundary
moves to capabilities/default.json's http:default scope, wildcarded so an
operator-chosen host is actually reachable. Adds a "Change server" control
in Setup (desktop-only) to repoint an already-configured install.

While tracing the desktop auth path for this: tauri-plugin-http's fetch()
runs through Rust's reqwest, which keeps its own cookie jar separate from
the webview, so document.cookie on tauri://localhost never sees the
parking_csrf cookie the server sets (open upstream bug,
tauri-apps/tauri#13045/#11518). This means the desktop app has likely been
silently sending no CSRF header on every mutation since the shell was
first built — pre-existing, independent of this change. Fixed by having
sessionView() (routes/auth.ts) also echo the CSRF value in the login/me
JSON body; the desktop client stashes it in memory and echoes that instead
of reading document.cookie. assertCsrf() itself is untouched.

Verified end-to-end against a real LAN-bound dev server: login returns a
csrfToken matching the cookie, a mutation using the body-sourced token in
X-CSRF-Token succeeds (200), and the same mutation without it still
correctly 403s.

apps/web/src/lib/backend-config.ts

@@ -0,0 +1,88 @@
+// Desktop-only: the operator-configured backend origin (host:port of the
+// Fastify server this install talks to), persisted across restarts.
+//
+// The desktop shell is a generic .deb/.AppImage — it is NOT built for one
+// specific booth, so the backend address can't be baked in at build time
+// (that was the old VITE_API_BASE approach; a rebuild was needed to point the
+// same installer at a different appliance). Instead the operator enters it
+// once in the ConnectScreen (shown before login whenever nothing usable is
+// stored yet) and it's saved to a JSON file in the OS config dir via
+// tauri-plugin-store, read back on every launch before any API call.
+//
+// Browser build: this module is never reached (inTauri() gates every call
+// site — see origin.ts), so there is no browser equivalent or fallback here.
+
+import type { Store } from "@tauri-apps/plugin-store";
+
+const STORE_FILE = "backend-config.json";
+const KEY = "backendUrl";
+
+let storeHandle: Store | null = null;
+async function getStore(): Promise<Store> {
+  if (!storeHandle) {
+    const { load } = await import("@tauri-apps/plugin-store");
+    storeHandle = await load(STORE_FILE, { autoSave: true });
+  }
+  return storeHandle;
+}
+
+/** The saved backend origin (no trailing slash), or null if never configured.
+ *  Desktop only — throws if called from a browser build. */
+export async function loadBackendUrl(): Promise<string | null> {
+  const store = await getStore();
+  const v = await store.get<string>(KEY);
+  return typeof v === "string" && v.length > 0 ? v.replace(/\/$/, "") : null;
+}
+
+/** Persist a new backend origin (validated + reachable — call testBackendUrl
+ *  first). Takes effect immediately for future platformFetch/wsUrl calls. */
+export async function saveBackendUrl(url: string): Promise<void> {
+  const store = await getStore();
+  await store.set(KEY, url.replace(/\/$/, ""));
+  await store.save();
+}
+
+/** Clear the saved backend (forces the ConnectScreen back up next launch). */
+export async function clearBackendUrl(): Promise<void> {
+  const store = await getStore();
+  await store.delete(KEY);
+  await store.save();
+}
+
+export interface BackendCheck {
+  ok: boolean;
+  /** "unreachable" (network/DNS/refused) | "bad_response" (reachable, not our API). */
+  reason?: "unreachable" | "bad_response";
+  detail?: string;
+}
+
+/** Probe a candidate origin by hitting /api/version. That route is behind
+ *  requirePermission("site:read") (session cookie + site:read — see
+ *  apps/server/src/routes/site.ts), so a pre-login probe can never get a 2xx;
+ *  we're not checking "is this reachable and mine to use", only "is something
+ *  that speaks our Fastify auth protocol listening here" — a 401 (missing/bad
+ *  JWT) or 403 (valid session, wrong permission) from THIS specific route is
+ *  as strong a signal of that as a 200 would be, and both are expected outcomes
+ *  pre-login. Uses the same tauri-plugin-http path platformFetch does (raw
+ *  fetch from the webview can't reach an arbitrary LAN host — mixed content,
+ *  see origin.ts). */
+export async function testBackendUrl(url: string): Promise<BackendCheck> {
+  const origin = url.replace(/\/$/, "");
+  try {
+    const { fetch: tauriFetch } = await import("@tauri-apps/plugin-http");
+    const res = await tauriFetch(`${origin}/api/version`, {
+      method: "GET",
+      signal: AbortSignal.timeout(5000),
+    });
+    if (!res.ok && res.status !== 401 && res.status !== 403) {
+      return { ok: false, reason: "bad_response", detail: `HTTP ${res.status}` };
+    }
+    return { ok: true };
+  } catch (err) {
+    return {
+      ok: false,
+      reason: "unreachable",
+      detail: err instanceof Error ? err.message : String(err),
+    };
+  }
+}

apps/web/src/lib/desktop-updater.ts

@@ -20,11 +20,7 @@
 // LogsViewer.tsx without needing a terminal or devtools at all.
 
 import { logClient } from "./logger.js";
-
-/** True when running inside the Tauri webview (not a normal browser). */
-function inTauri(): boolean {
-  return typeof window !== "undefined" && "__TAURI_INTERNALS__" in window;
-}
+import { inTauri } from "./tauri-env.js";
 
 export interface UpdatePrompt {
   /** Newer version string offered by the server. */

apps/web/src/lib/i18n/en.ts

@@ -42,6 +42,20 @@ export const en: Catalog = {
     signIn: "Sign in",
     signingIn: "Signing in…",
   },
+  connect: {
+    title: "Connect to server",
+    hint: "Enter the address of the parking system server for this booth.",
+    serverAddress: "Server address",
+    test: "Test",
+    testing: "Testing…",
+    save: "Save & continue",
+    saving: "Saving…",
+    testOk: "Reachable — this looks like a Parking System server.",
+    testUnreachable: "Could not reach this address.",
+    testBadResponse: "Reachable, but this doesn't look like a Parking System server.",
+    changeServer: "Change server",
+    changeServerConfirm: "This signs you out and asks for a new server address on next launch. Continue?",
+  },
   update: {
     available: "Update available",
     prompt: "Version {{version}} is available. Install now and restart?",

apps/web/src/lib/i18n/sq.ts

@@ -45,6 +45,20 @@ export const sq = {
     signIn: "Hyr",
     signingIn: "Duke hyrë…",
   },
+  connect: {
+    title: "Lidhu me serverin",
+    hint: "Vendos adresën e serverit të sistemit të parkimit për këtë kabinë.",
+    serverAddress: "Adresa e serverit",
+    test: "Testo",
+    testing: "Duke testuar…",
+    save: "Ruaj & vazhdo",
+    saving: "Duke ruajtur…",
+    testOk: "I arritshëm — duket si server i Sistemit të Parkimit.",
+    testUnreachable: "Nuk u arrit kjo adresë.",
+    testBadResponse: "I arritshëm, por nuk duket si server i Sistemit të Parkimit.",
+    changeServer: "Ndrysho serverin",
+    changeServerConfirm: "Kjo do t'ju dalë nga sesioni dhe do kërkojë adresë të re serveri në hapjen tjetër. Vazhdo?",
+  },
   update: {
     available: "Përditësim i disponueshëm",
     prompt: "Versioni {{version}} është i disponueshëm. Ta instaloj tani dhe ta rinis?",

apps/web/src/lib/origin.ts

@@ -3,16 +3,19 @@
 // In a browser (dev via the Vite proxy, or prod where Fastify serves the built
 // SPA) this is EMPTY — requests stay relative (`/api/...`) and same-origin, so
 // nothing changes. The Tauri desktop shell (apps/desktop) serves the bundled
-// SPA from `tauri://localhost`, which has no backend and no proxy; there we set
-// VITE_API_BASE to the appliance's Fastify origin (e.g. http://127.0.0.1:3000)
-// at build time so /api and the live WS feed resolve to the real server.
+// SPA from `tauri://localhost`, which has no backend and no proxy; there the
+// operator enters the appliance's Fastify origin (e.g. http://192.168.1.50:3000)
+// once in the ConnectScreen and it's persisted via tauri-plugin-store (see
+// backend-config.ts) — a RUNTIME value, not a build-time one, since the same
+// installer is used across every booth and the backend can move (new box, new
+// IP) without a rebuild. main.tsx calls initApiBase() before the app mounts.
 //
 // Keep this the SINGLE source for the backend origin — api.ts and the live-feed
 // WebSocket both read it, so the web app and the desktop shell stay identical
-// except for this one build-time value.
+// except for this one runtime value.
 //
 // platformFetch(): WebKitGTK treats tauri://localhost as a SECURE origin, so a
-// plain http://127.0.0.1:3000 fetch() from inside it is blocked as mixed
+// plain http://192.168.1.50:3000 fetch() from inside it is blocked as mixed
 // content (a WebKit limitation — CSP's connect-src does NOT override this;
 // found 2026-09-03 as "Load failed" on every desktop request). Inside Tauri we
 // dynamically import @tauri-apps/plugin-http's fetch, which routes the request
@@ -20,8 +23,29 @@
 // the check entirely. Browser build never imports the plugin (dynamic import,
 // same pattern as desktop-updater.ts).
 
-/** Backend HTTP origin, no trailing slash. Empty string = same-origin/relative. */
-export const API_BASE: string = (import.meta.env.VITE_API_BASE ?? "").replace(/\/$/, "");
+import { inTauri } from "./tauri-env.js";
+
+/** Backend HTTP origin, no trailing slash. Empty string = same-origin/relative
+ *  (browser) or not-yet-configured (desktop, before the ConnectScreen runs). */
+export let API_BASE: string = "";
+
+/** Desktop only: load the persisted backend URL (if any) before the app
+ *  mounts, so the very first fetchMe() call already has the right origin.
+ *  No-op in the browser. Returns the loaded value (null = not configured yet,
+ *  meaning main.tsx should show the ConnectScreen instead of the normal app). */
+export async function initApiBase(): Promise<string | null> {
+  if (!inTauri()) return null;
+  const { loadBackendUrl } = await import("./backend-config.js");
+  const saved = await loadBackendUrl();
+  if (saved) API_BASE = saved;
+  return saved;
+}
+
+/** Desktop only: change the backend origin at runtime (after the operator
+ *  saves a new one in Settings) without requiring a full app restart. */
+export function setApiBase(url: string): void {
+  API_BASE = url.replace(/\/$/, "");
+}
 
 /** Resolve an API path to a full URL (or a relative path when API_BASE is empty). */
 export function apiUrl(path: string): string {
@@ -38,10 +62,7 @@ export function wsUrl(path: string): string {
   return `${proto}//${window.location.host}${path}`;
 }
 
-/** True when running inside the Tauri webview (not a normal browser). */
-export function inTauri(): boolean {
-  return typeof window !== "undefined" && "__TAURI_INTERNALS__" in window;
-}
+export { inTauri };
 
 /**
  * fetch(), but routed through @tauri-apps/plugin-http inside the desktop

apps/web/src/lib/platform-ws.ts

@@ -17,6 +17,8 @@
 // Browser build: plain pass-through to the real WebSocket (this file's
 // createPlatformSocket is only called from inside inTauri() callers).
 
+import { inTauri } from "./tauri-env.js";
+
 export interface PlatformSocket {
   onopen: (() => void) | null;
   onmessage: ((ev: { data: string }) => void) | null;
@@ -97,11 +99,6 @@ class TauriSocketAdapter implements PlatformSocket {
   }
 }
 
-/** True when running inside the Tauri webview (not a normal browser). */
-function inTauri(): boolean {
-  return typeof window !== "undefined" && "__TAURI_INTERNALS__" in window;
-}
-
 /** Open a live-feed socket, routed through the Tauri WebSocket plugin inside the
  *  desktop shell (mixed-content workaround), or the native WebSocket in a browser. */
 export function createPlatformSocket(url: string): PlatformSocket {

apps/web/src/lib/tauri-env.ts

@@ -0,0 +1,6 @@
+/** True when running inside the Tauri webview (not a normal browser). Single
+ *  source for this check — origin.ts, platform-ws.ts, desktop-updater.ts, and
+ *  backend-config.ts all gate their Tauri-only code paths on it. */
+export function inTauri(): boolean {
+  return typeof window !== "undefined" && "__TAURI_INTERNALS__" in window;
+}