feat(prefs): per-user UI font scale (A−/A+), saved to the profile

A header A−/value/A+ control scales the whole UI, persisted per user and
restored on login from any booth — cloning the theme-pref pattern end to end.

- DB: users.font_scale (migration 0014; percent, 100 = base, NOT NULL default).
- Server: PUT /api/auth/font-scale (auth-guarded; clamps to 80–160, snaps to a
  10-step); fontScale flows through sessionView → login + /me.
- Client: setFontScalePref + applyFontScale; applied in App alongside theme;
  FontScaleToggle in the header; i18n sq+en.

Scaling uses CSS `zoom` on the root, NOT root font-size: the app's type is pinned
in px (text-[12px] etc., ~230 spots), which a font-size change would not scale —
so the dense Active-sessions / Live-feed logs stayed tiny. `zoom` scales
everything uniformly (text, spacing, icons) like the browser's Ctrl+/−, which is
the readability win for operators who need larger text.

Tests: 4 font-scale auth-route cases (persist + /me, clamp/snap, 400, default-100).
Full workspace build/lint/test green.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/App.tsx

@@ -5,7 +5,7 @@ import { fetchMe, type SessionUser } from "./api.js";
 import { Login } from "./Login.js";
 import { queryClient } from "./lib/query.js";
 import { setLanguage } from "./lib/i18n/index.js";
-import { applyTheme } from "./lib/theme.js";
+import { applyTheme, applyFontScale } from "./lib/theme.js";
 import { router } from "./router.js";
 
 // App root: bootstraps the session (cookie-based, from /api/auth/me), then hands
@@ -24,15 +24,17 @@ export function App() {
       .finally(() => setLoading(false));
   }, []);
 
-  // Apply the signed-in user's preferred language + theme whenever they resolve/
-  // change (login, bootstrap, or a toggle). Albanian + dark are the defaults before
-  // auth resolves; on logout, fall back to dark so the Login screen is consistent.
+  // Apply the signed-in user's preferred language + theme + font scale whenever they
+  // resolve/change (login, bootstrap, or a toggle). Albanian + dark + 100% are the defaults
+  // before auth resolves; on logout, fall back so the Login screen is consistent.
   useEffect(() => {
     if (user) {
       setLanguage(user.language);
       applyTheme(user.theme);
+      applyFontScale(user.fontScale);
     } else {
       applyTheme("dark");
+      applyFontScale(100);
     }
   }, [user]);