feat: unified photo provider abstraction layer (#584)

Introduce trek_photos as central photo registry. Frontend uses
/api/photos/:id/:kind instead of provider-specific URLs. Adding
a new photo provider is now backend-only work.

- New trek_photos table (migration 98) with photo_id FK in
  trip_photos and journey_photos
- Unified /api/photos/:id/thumbnail|original|info endpoint
- photoResolverService for central resolution and streaming
- ProviderPicker: add "All Photos" tab, rename tabs, fix i18n
- Localize all hardcoded strings in JourneyDetailPage (14 langs)
- Fix date formatting to use browser locale instead of hardcoded 'en'
- Journey stats as styled tile cards

server/src/services/memories/photoResolverService.ts

@@ -0,0 +1,141 @@
+import { Response } from 'express';
+import path from 'path';
+import fs from 'fs';
+import { db } from '../../db/database';
+import type { TrekPhoto } from '../../types';
+import { streamImmichAsset, getAssetInfo as getImmichAssetInfo } from './immichService';
+import { streamSynologyAsset, getSynologyAssetInfo } from './synologyService';
+import type { ServiceResult, AssetInfo } from './helpersService';
+import { fail, success } from './helpersService';
+
+// ── Lookup / Register ────────────────────────────────────────────────────
+
+export function getOrCreateTrekPhoto(
+  provider: string,
+  assetId: string,
+  ownerId: number,
+): number {
+  const existing = db.prepare(
+    'SELECT id FROM trek_photos WHERE provider = ? AND asset_id = ? AND owner_id = ?'
+  ).get(provider, assetId, ownerId) as { id: number } | undefined;
+  if (existing) return existing.id;
+
+  const res = db.prepare(
+    'INSERT INTO trek_photos (provider, asset_id, owner_id) VALUES (?, ?, ?)'
+  ).run(provider, assetId, ownerId);
+  return Number(res.lastInsertRowid);
+}
+
+export function getOrCreateLocalTrekPhoto(
+  filePath: string,
+  thumbnailPath?: string | null,
+  width?: number | null,
+  height?: number | null,
+): number {
+  const existing = db.prepare(
+    "SELECT id FROM trek_photos WHERE provider = 'local' AND file_path = ?"
+  ).get(filePath) as { id: number } | undefined;
+  if (existing) return existing.id;
+
+  const res = db.prepare(
+    'INSERT INTO trek_photos (provider, file_path, thumbnail_path, width, height) VALUES (?, ?, ?, ?, ?)'
+  ).run('local', filePath, thumbnailPath || null, width || null, height || null);
+  return Number(res.lastInsertRowid);
+}
+
+export function resolveTrekPhoto(photoId: number): TrekPhoto | null {
+  return db.prepare('SELECT * FROM trek_photos WHERE id = ?').get(photoId) as TrekPhoto | undefined || null;
+}
+
+// ── Streaming ────────────────────────────────────────────────────────────
+
+export async function streamPhoto(
+  res: Response,
+  userId: number,
+  photoId: number,
+  kind: 'thumbnail' | 'original',
+): Promise<void> {
+  const photo = resolveTrekPhoto(photoId);
+  if (!photo) {
+    res.status(404).json({ error: 'Photo not found' });
+    return;
+  }
+
+  switch (photo.provider) {
+    case 'local': {
+      const filePath = path.join(__dirname, '../../../uploads', photo.file_path!);
+      if (!fs.existsSync(filePath)) {
+        res.status(404).json({ error: 'File not found' });
+        return;
+      }
+      res.set('Cache-Control', 'public, max-age=86400');
+      res.sendFile(filePath);
+      return;
+    }
+    case 'immich': {
+      await streamImmichAsset(res, userId, photo.asset_id!, kind, photo.owner_id!);
+      return;
+    }
+    case 'synologyphotos': {
+      await streamSynologyAsset(res, userId, photo.owner_id!, photo.asset_id!, kind);
+      return;
+    }
+    default:
+      res.status(400).json({ error: `Unknown provider: ${photo.provider}` });
+  }
+}
+
+// ── Asset Info ────────────────────────────────────────────────────────────
+
+export async function getPhotoInfo(
+  userId: number,
+  photoId: number,
+): Promise<ServiceResult<AssetInfo>> {
+  const photo = resolveTrekPhoto(photoId);
+  if (!photo) return fail('Photo not found', 404);
+
+  switch (photo.provider) {
+    case 'local': {
+      return success({
+        id: String(photo.id),
+        takenAt: photo.created_at,
+        city: null,
+        country: null,
+        width: photo.width,
+        height: photo.height,
+        fileName: photo.file_path?.split('/').pop() || null,
+      } as AssetInfo);
+    }
+    case 'immich': {
+      const result = await getImmichAssetInfo(userId, photo.asset_id!, photo.owner_id!);
+      if (result.error) return fail(result.error, result.status || 500);
+      return success(result.data as AssetInfo);
+    }
+    case 'synologyphotos': {
+      return getSynologyAssetInfo(userId, photo.asset_id!, photo.owner_id!);
+    }
+    default:
+      return fail(`Unknown provider: ${photo.provider}`, 400);
+  }
+}
+
+// ── Update provider on existing trek_photo (for Immich upload sync) ─────
+
+export function setTrekPhotoProvider(
+  trekPhotoId: number,
+  provider: string,
+  assetId: string,
+  ownerId: number,
+): void {
+  db.prepare(
+    'UPDATE trek_photos SET provider = ?, asset_id = ?, owner_id = ? WHERE id = ?'
+  ).run(provider, assetId, ownerId, trekPhotoId);
+}
+
+// ── Delete local file for a trek_photo ──────────────────────────────────
+
+export function getTrekPhotoFilePath(photoId: number): string | null {
+  const photo = resolveTrekPhoto(photoId);
+  if (!photo || photo.provider !== 'local' || !photo.file_path) return null;
+  return path.join(__dirname, '../../../uploads', photo.file_path);
+}