fix(synology): resolve pagination offset using correct size before computing page offset

The `size` → `limit` assignment was evaluated after `page * limit`, causing
the offset to be computed using the hardcoded default (100) instead of the
caller-supplied page size. Swapping the two `if` blocks ensures `limit` is
resolved from `size` first so the offset is always `(page-1) * size`.

Adds SYNO-025 and SYNO-026 integration tests that capture the raw Synology
API body and assert `offset` and `limit` are forwarded correctly.

server/src/routes/memories/synology.ts

@@ -100,8 +100,8 @@ router.post('/search', authenticate, async (req: Request, res: Response) => {
     const page = _parseNumberBodyField(body.page, 1) - 1;
     let limit = _parseNumberBodyField(body.limit, 100);
     const size = _parseNumberBodyField(body.size, 0);
-    if(page > 0) offset = page*limit;
-    if(size > 0) limit = size;
+    if (size > 0) limit = size;
+    if (page > 0) offset = page * limit;
 
     handleServiceResult(res, await searchSynologyPhotos(
         authReq.user.id,

server/tests/integration/memories-synology.test.ts

@@ -843,6 +843,83 @@ describe('Synology searchSynologyPhotos date range', () => {
   });
 });
 
+// ── Search pagination ─────────────────────────────────────────────────────────
+
+describe('Synology search pagination', () => {
+  it('SYNO-025 — POST /search with { page: 2, size: 50 } sends offset=50 and limit=50 to Synology API', async () => {
+    const { user } = createUser(testDb);
+    setSynologyCredentials(testDb, user.id, 'https://synology.example.com', 'admin', 'pass');
+
+    let capturedBody: URLSearchParams | null = null;
+    vi.mocked(safeFetch)
+      .mockResolvedValueOnce({
+        // login
+        ok: true, status: 200,
+        headers: { get: () => 'application/json' },
+        json: async () => ({ success: true, data: { sid: 'fake-sid' } }),
+        body: null,
+      } as any)
+      .mockImplementationOnce((_url: string, init?: any) => {
+        capturedBody = init?.body instanceof URLSearchParams
+          ? init.body
+          : new URLSearchParams(String(init?.body ?? ''));
+        return Promise.resolve({
+          ok: true, status: 200,
+          headers: { get: () => 'application/json' },
+          json: async () => ({ success: true, data: { list: [] } }),
+          body: null,
+        } as any);
+      });
+
+    const res = await request(app)
+      .post(`${SYNO}/search`)
+      .set('Cookie', authCookie(user.id))
+      .send({ page: 2, size: 50 });
+
+    expect(res.status).toBe(200);
+    expect(capturedBody).not.toBeNull();
+    // With the fix: limit=50 is resolved first, then offset = (2-1)*50 = 50
+    expect(capturedBody!.get('offset')).toBe('50');
+    expect(capturedBody!.get('limit')).toBe('50');
+  });
+
+  it('SYNO-026 — POST /search with { page: 3, size: 25 } sends offset=50 and limit=25 to Synology API', async () => {
+    const { user } = createUser(testDb);
+    setSynologyCredentials(testDb, user.id, 'https://synology.example.com', 'admin', 'pass');
+
+    let capturedBody: URLSearchParams | null = null;
+    vi.mocked(safeFetch)
+      .mockResolvedValueOnce({
+        ok: true, status: 200,
+        headers: { get: () => 'application/json' },
+        json: async () => ({ success: true, data: { sid: 'fake-sid' } }),
+        body: null,
+      } as any)
+      .mockImplementationOnce((_url: string, init?: any) => {
+        capturedBody = init?.body instanceof URLSearchParams
+          ? init.body
+          : new URLSearchParams(String(init?.body ?? ''));
+        return Promise.resolve({
+          ok: true, status: 200,
+          headers: { get: () => 'application/json' },
+          json: async () => ({ success: true, data: { list: [] } }),
+          body: null,
+        } as any);
+      });
+
+    const res = await request(app)
+      .post(`${SYNO}/search`)
+      .set('Cookie', authCookie(user.id))
+      .send({ page: 3, size: 25 });
+
+    expect(res.status).toBe(200);
+    expect(capturedBody).not.toBeNull();
+    // page 3 → page index = 2 (after subtracting 1), offset = 2 * 25 = 50
+    expect(capturedBody!.get('offset')).toBe('50');
+    expect(capturedBody!.get('limit')).toBe('25');
+  });
+});
+
 // ── SSRF catch branch in _fetchSynologyJson ────────────────────────────────────
 
 describe('Synology SSRF blocked error handling', () => {