test(upload): unit tests for backgroundProcessor + processPhoto

Cover the two new pieces of the async pipeline:

backgroundProcessor.claimNextPhoto
  - returns null when no pending rows
  - returns the row + flips status under postgres FOR UPDATE SKIP LOCKED
  - returns null when SQLite UPDATE-with-guard loses the race
  - returns the row when the SQLite guard wins

photoProcessor.processPhoto
  - happy path: writes thumbnail / dimensions / EXIF capture date and
    marks 'complete'; fires watermark queue + photo.uploaded webhook
    with the right payload
  - video path: writes ffmpeg duration / codec / dimensions; does NOT
    queue watermark (image-only)
  - throws cleanly when the photo row no longer exists

Mocks db / imageProcessor / videoProcessor / storage / sharp /
watermarkGeneratorService / webhookService / logger so the tests run
without a real DB or any image library calls — fast and deterministic.

backend/__tests__/services/photoProcessor.processPhoto.test.js

@@ -0,0 +1,216 @@
+/**
+ * Unit tests for photoProcessor.processPhoto — the worker-mode entry
+ * point that runs after a row has been claimed by the background
+ * processor. Mocks every external dependency and validates the
+ * happy-path DB updates and side-effect ordering.
+ *
+ * jest.mock factories are evaluated before any local variables exist,
+ * so collaborators are kept inside the mock factories themselves and
+ * the test reaches into them via require() once they're set up.
+ */
+
+const path = require('path');
+
+jest.mock('../../src/database/db', () => {
+  const recorded = { whereCalls: [], updateCalls: [] };
+  let pendingWhere = null;
+  const photosState = { row: null };
+  const eventsState = { row: null };
+
+  function makePhotoQuery() {
+    return {
+      where(args) {
+        pendingWhere = args;
+        recorded.whereCalls.push(args);
+        return this;
+      },
+      async first() {
+        return photosState.row;
+      },
+      async update(data) {
+        recorded.updateCalls.push({ where: pendingWhere, data });
+        return 1;
+      },
+    };
+  }
+
+  function makeEventsQuery() {
+    return {
+      where() {
+        return this;
+      },
+      async first() {
+        return eventsState.row;
+      },
+    };
+  }
+
+  function dbFn(table) {
+    if (table === 'photos') return makePhotoQuery();
+    if (table === 'events') return makeEventsQuery();
+    throw new Error(`Unexpected table: ${table}`);
+  }
+  dbFn.client = { config: { client: 'pg' } };
+
+  return {
+    db: dbFn,
+    __setPhoto: (row) => { photosState.row = row; },
+    __setEvent: (row) => { eventsState.row = row; },
+    __reset: () => {
+      recorded.whereCalls = [];
+      recorded.updateCalls = [];
+      photosState.row = null;
+      eventsState.row = null;
+    },
+    __recorded: () => recorded,
+  };
+});
+
+jest.mock('../../src/services/imageProcessor', () => {
+  const mockGenerateThumbnail = jest.fn();
+  const mockExtractCaptureDate = jest.fn();
+  return {
+    generateThumbnail: mockGenerateThumbnail,
+    extractCaptureDate: mockExtractCaptureDate,
+    withLocalCopy: jest.fn(async (key, fn) =>
+      fn(`/tmp/local-copy-${require('path').basename(key)}`)
+    ),
+  };
+});
+
+jest.mock('../../src/services/videoProcessor', () => ({
+  processUploadedVideo: jest.fn(),
+  isVideoMimeType: (mime) => typeof mime === 'string' && mime.startsWith('video/'),
+}));
+
+jest.mock('../../src/services/storage', () => ({ getStorage: jest.fn() }));
+
+jest.mock('../../src/services/photoResolver', () => ({
+  resolvePhotoStorageKey: jest.fn(
+    (event, photo) => `events/active/${event.slug}/${photo.filename}`
+  ),
+}));
+
+jest.mock('../../src/utils/filenameSanitizer', () => ({
+  generatePhotoFilename: jest.fn(() => 'whatever.jpg'),
+}));
+
+jest.mock('../../src/services/watermarkGeneratorService', () => ({
+  generateForPhoto: jest.fn(() => Promise.resolve()),
+}));
+
+jest.mock('../../src/services/webhookService', () => ({
+  fire: jest.fn(() => Promise.resolve()),
+}));
+
+jest.mock('../../src/utils/logger', () => ({
+  warn: jest.fn(),
+  error: jest.fn(),
+  info: jest.fn(),
+  debug: jest.fn(),
+}));
+
+// Stub sharp so we don't actually read any image off disk.
+jest.mock('sharp', () => {
+  const mock = jest.fn(() => ({
+    metadata: jest.fn(async () => ({ width: 1920, height: 1080 })),
+  }));
+  return mock;
+});
+
+const dbModule = require('../../src/database/db');
+const imageProcessor = require('../../src/services/imageProcessor');
+const videoProcessor = require('../../src/services/videoProcessor');
+const watermarkService = require('../../src/services/watermarkGeneratorService');
+const webhookService = require('../../src/services/webhookService');
+
+beforeEach(() => {
+  dbModule.__reset();
+  jest.clearAllMocks();
+});
+
+describe('photoProcessor.processPhoto', () => {
+  it('marks an image complete with thumbnail and dimensions', async () => {
+    dbModule.__setPhoto({
+      id: 101,
+      event_id: 5,
+      filename: 'wedding-001.jpg',
+      original_filename: 'IMG_0001.jpg',
+      mime_type: 'image/jpeg',
+      media_type: 'image',
+      size_bytes: 12345,
+      captured_at: null,
+      processing_status: 'processing',
+    });
+    dbModule.__setEvent({ id: 5, slug: 'wedding', event_name: 'Wedding' });
+
+    imageProcessor.extractCaptureDate.mockResolvedValueOnce('2026-04-25T12:00:00Z');
+    imageProcessor.generateThumbnail.mockResolvedValueOnce('thumbnails/thumb_wedding-001.jpg');
+
+    const { processPhoto } = require('../../src/services/photoProcessor');
+    await processPhoto(101);
+
+    const finalUpdate = dbModule.__recorded().updateCalls.pop();
+    expect(finalUpdate.data.processing_status).toBe('complete');
+    expect(finalUpdate.data.processing_error).toBeNull();
+    expect(finalUpdate.data.thumbnail_path).toBe('thumbnails/thumb_wedding-001.jpg');
+    expect(finalUpdate.data.width).toBe(1920);
+    expect(finalUpdate.data.height).toBe(1080);
+    expect(finalUpdate.data.captured_at).toBe('2026-04-25T12:00:00Z');
+
+    expect(watermarkService.generateForPhoto).toHaveBeenCalledWith(101);
+    expect(webhookService.fire).toHaveBeenCalledWith(
+      'photo.uploaded',
+      expect.objectContaining({
+        event: expect.objectContaining({ slug: 'wedding' }),
+        photo: expect.objectContaining({ id: 101, filename: 'wedding-001.jpg' }),
+      })
+    );
+  });
+
+  it('handles videos with ffmpeg metadata path', async () => {
+    dbModule.__setPhoto({
+      id: 202,
+      event_id: 9,
+      filename: 'wedding-video-001.mp4',
+      original_filename: 'movie.mp4',
+      mime_type: 'video/mp4',
+      media_type: 'video',
+      size_bytes: 99999,
+      captured_at: null,
+    });
+    dbModule.__setEvent({ id: 9, slug: 'wedding', event_name: 'Wedding' });
+
+    videoProcessor.processUploadedVideo.mockResolvedValueOnce({
+      thumbnailKey: 'thumbnails/thumb_wedding-video-001.jpg',
+      metadata: {
+        duration: 12.5,
+        videoCodec: 'h264',
+        audioCodec: 'aac',
+        width: 1280,
+        height: 720,
+      },
+    });
+
+    const { processPhoto } = require('../../src/services/photoProcessor');
+    await processPhoto(202);
+
+    const finalUpdate = dbModule.__recorded().updateCalls.pop();
+    expect(finalUpdate.data.processing_status).toBe('complete');
+    expect(finalUpdate.data.duration).toBe(12.5);
+    expect(finalUpdate.data.video_codec).toBe('h264');
+    expect(finalUpdate.data.thumbnail_path).toBe('thumbnails/thumb_wedding-video-001.jpg');
+
+    // Watermark queue is image-only.
+    expect(watermarkService.generateForPhoto).not.toHaveBeenCalled();
+  });
+
+  it('throws when the photo row no longer exists', async () => {
+    dbModule.__setPhoto(null);
+    dbModule.__setEvent({ id: 1 });
+    const { processPhoto } = require('../../src/services/photoProcessor');
+    await expect(processPhoto(999)).rejects.toThrow(/Photo 999 not found/);
+  });
+});
+
+void path; // referenced indirectly via mocks