feat(setup): "Test ANPR" probe on ANPR-enabled cameras

Adds a bottom-of-modal "Test ANPR" button (shown only when a camera's
Plate recognition opt-in is checked) that captures a live snapshot off
the camera and runs it through the vision service, reporting the plate
read + confidence + elapsed time, or which stage failed.

- New POST /api/setup/test-anpr: builds the camera from the unsaved
  config (no DB write/device change, like /test), captures a snapshot,
  runs vision.analyze. Fail-soft like the runtime path (snapshot.ts):
  camera/vision failures are reported results, never a 500.
- Thread the existing VisionClient into setupRoutes; add an isCamera()
  type guard to @parking/devices.
- Web: testAnpr() client + AnprTestResult; button, hint, result line.
- i18n keys in sq + en (Catalog parity).

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

packages/devices/src/interfaces.ts

@@ -173,6 +173,10 @@ export interface CameraDevice extends Device {
   captureSnapshot(ctx: SnapshotContext): Promise<Snapshot>;
 }
 
+export function isCamera(device: Device): device is Device & CameraDevice {
+  return typeof (device as Partial<CameraDevice>).captureSnapshot === "function";
+}
+
 export interface SnapshotContext {
   readonly direction: "entry" | "exit";
 }