feat(devices): camera clock sync via ISAPI — heal the 1970 power-cut reset

park-buzi field observation: after a power cut the Hikvision cameras
reboot at the 1970 epoch (no/dead RTC battery, no NTP) and stay there
until a human logs into the web UI (which silently pushes the browser
clock) — corrupting the snapshot OSD timestamps (the evidence trail) and
ANPR push times meanwhile.

The host is the site's time authority (offline-first, no NTP infra):

- Device monitor triggers a sync at each camera's offline→ready edge —
  exactly the power-restored moment — plus a 24h backstop; the attempt
  is stamped before the async call so a failing camera retries at
  backstop cadence, never every poll.
- HikvisionCamera.syncClock: GET /ISAPI/System/time; drift ≤60s → leave
  alone; beyond (or unparseable = infinite drift) → PUT timeMode=manual
  with the site wall-clock now WITH explicit utc offset
  (localIsoWithOffset), echoing the camera's timeZone verbatim — correct
  the clock, never fight its tz/DST config.
- Jumps >1h (the power-cut signature) log warn (persisted to app_logs);
  small corrections info. Capability-guarded (isClockSyncable) —
  hikvision only; dahua's CGI has no such endpoint.
- http-digest generalised to digestRequest (GET/PUT/POST + body); the
  handshake was already method-aware. digestGet delegates unchanged.

8 new tests: in-sync no-op, 1970 PUT shape (manual + host instant +
echoed tz), unparseable→sync, failed-set surfaces, dahua non-capability,
DST-both-sides pins on the offset formatter.

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

apps/server/src/device-monitor.ts

@@ -1,9 +1,10 @@
 import type { FastifyBaseLogger } from "fastify";
 import { devices, type Db, type DeviceRow } from "@parking/db";
-import { isMonitorable, registry } from "@parking/devices";
+import { isClockSyncable, isMonitorable, registry, type Device } from "@parking/devices";
 import { deviceEvents, type DeviceStatusEvent } from "./device-events.js";
 import { directionOf, relaysOf } from "./device-resolve.js";
 import type { VisionClient } from "./vision-client.js";
+import { siteTz } from "./subscription-window.js";
 
 /** Synthetic device id for the vision service in the status footer (it's a service,
  *  not a device row, but shares the footer's traffic-light + WS plumbing). */
@@ -23,6 +24,40 @@ const VISION_STATUS_ID = "vision-service";
 
 const POLL_MS = Number(process.env.DEVICE_POLL_MS ?? 8000);
 
+// Camera clock sync (Hikvision loses its clock on power cuts — reboots at the 1970
+// epoch until a human logs into its web UI). The monitor re-syncs from the HOST
+// clock (the site's offline time authority) at the offline→ready edge — exactly the
+// power-restored moment — plus a daily backstop; drift under the threshold is left
+// alone. See wiki/entities/lpr-camera.md (clock sync).
+const CLOCK_SYNC_BACKSTOP_MS = 24 * 60 * 60 * 1000;
+const CLOCK_MAX_DRIFT_SEC = 60;
+
+/** The site's wall-clock now as ISO WITH utc offset (e.g. 2026-07-07T15:30:22+02:00)
+ *  — what ISAPI's localTime wants. Derived via Intl for the site tz (no dep). */
+export function localIsoWithOffset(tz: string, at = new Date()): string {
+  const fmt = new Intl.DateTimeFormat("en-CA", {
+    timeZone: tz,
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+    hour: "2-digit",
+    minute: "2-digit",
+    second: "2-digit",
+    hourCycle: "h23",
+  });
+  const p = Object.fromEntries(fmt.formatToParts(at).map((x) => [x.type, x.value]));
+  const wallAsUtcMs = Date.UTC(
+    Number(p.year), Number(p.month) - 1, Number(p.day),
+    Number(p.hour), Number(p.minute), Number(p.second),
+  );
+  const offMin = Math.round((wallAsUtcMs - at.getTime()) / 60_000);
+  const sign = offMin < 0 ? "-" : "+";
+  const abs = Math.abs(offMin);
+  const hh = String(Math.floor(abs / 60)).padStart(2, "0");
+  const mm = String(abs % 60).padStart(2, "0");
+  return `${p.year}-${p.month}-${p.day}T${p.hour}:${p.minute}:${p.second}${sign}${hh}:${mm}`;
+}
+
 /**
  * The device's ROLE descriptor for the footer (never the vendor). Direction-style
  * tokens the client localises next to the category:
@@ -139,6 +174,7 @@ export class DeviceMonitor {
     };
 
     let next: DeviceStatusEvent;
+    let device: Device | null = null;
     const driver = registry.get(row.driverId);
     if (!driver) {
       // Configured against a driver that's no longer registered — surface it,
@@ -146,7 +182,7 @@ export class DeviceMonitor {
       next = { ...base, state: "offline", detail: "driver not registered", checkedAt: new Date().toISOString() };
     } else {
       try {
-        const device = driver.create(cfg as never);
+        device = driver.create(cfg as never);
         // Printers expose richer paper/cover/cutter status; everything else uses
         // the generic reachability probe. Both flatten to the same traffic-light.
         if (isMonitorable(device)) {
@@ -163,6 +199,33 @@ export class DeviceMonitor {
       }
     }
 
+    // Camera clock re-sync at the power-restored edge (prev offline/unknown →
+    // ready) + a daily backstop. Stamped BEFORE the async attempt so a failing
+    // camera is retried at backstop cadence, never every poll.
+    if (row.category === "camera" && next.state === "ready" && device && isClockSyncable(device)) {
+      const prev = this.#latest.get(row.id);
+      const cameBack = !prev || prev.state === "offline";
+      const last = this.#clockSyncedAt.get(row.id) ?? 0;
+      if (cameBack || Date.now() - last > CLOCK_SYNC_BACKSTOP_MS) {
+        this.#clockSyncedAt.set(row.id, Date.now());
+        const cam = device;
+        void (async () => {
+          try {
+            const r = await cam.syncClock(localIsoWithOffset(siteTz(this.#db)), CLOCK_MAX_DRIFT_SEC);
+            if (r.synced) {
+              // A large jump is the 1970 power-cut signature — warn (persisted) so
+              // the reboot stays visible; a small correction is routine info.
+              const msg = `device-monitor: camera ${row.id} clock synced (was ${r.driftSeconds ?? "unparseable"}s off)`;
+              if (r.driftSeconds == null || r.driftSeconds > 3600) this.#log.warn(msg);
+              else this.#log.info(msg);
+            }
+          } catch (err) {
+            this.#log.warn(`device-monitor: camera ${row.id} clock sync failed: ${(err as Error).message}`);
+          }
+        })();
+      }
+    }
+
     this.#publish(row.id, next);
   }
 
@@ -183,6 +246,9 @@ export class DeviceMonitor {
     });
   }
 
+  /** Per-camera timestamp of the last clock-sync ATTEMPT (backstop pacing). */
+  readonly #clockSyncedAt = new Map<string, number>();
+
   /** Cache + emit a status, but only when it CHANGED (state or detail). */
   #publish(id: string, next: DeviceStatusEvent): void {
     const prev = this.#latest.get(id);