perf(app): reduce redundant data fetching

Share bounded database pools across API repositories, consolidate sync and chat queries, and make mobile refreshes cache-aware and foreground-aware.

Add focused regression coverage, client freshness documentation, and repository agent role configuration.

apps/mobile/src/__tests__/lib/appForeground.test.ts

@@ -0,0 +1,36 @@
+import { AppState } from 'react-native';
+import { isForeground, isForegroundState, subscribeToForeground } from '@/lib/appForeground';
+
+describe('appForeground', () => {
+    afterEach(() => jest.restoreAllMocks());
+
+    it('treats only background and inactive as away', () => {
+        expect(isForegroundState('active')).toBe(true);
+        expect(isForegroundState('background')).toBe(false);
+        expect(isForegroundState('inactive')).toBe(false);
+        // Unknown states — including whatever a test harness leaves behind — must
+        // fail towards running, never towards disabling recurring work forever.
+        expect(isForegroundState(undefined)).toBe(true);
+        expect(isForegroundState('extension')).toBe(true);
+    });
+
+    it('reads the current state and reports transitions until unsubscribed', () => {
+        let emit: (state: string) => void = () => undefined;
+        const remove = jest.fn();
+        jest.spyOn(AppState, 'addEventListener').mockImplementation(((_: string, handler: (state: string) => void) => {
+            emit = handler;
+            return { remove } as never;
+        }) as never);
+
+        expect(isForeground()).toBe(isForegroundState(AppState.currentState));
+
+        const seen: boolean[] = [];
+        const unsubscribe = subscribeToForeground(value => seen.push(value));
+        emit('background');
+        emit('active');
+        expect(seen).toEqual([false, true]);
+
+        unsubscribe();
+        expect(remove).toHaveBeenCalled();
+    });
+});

apps/mobile/src/__tests__/lib/chatApi.test.ts

@@ -24,6 +24,18 @@ describe('chatApi', () => {
         expect(apiClient.get).toHaveBeenNthCalledWith(2, '/v1/matches/match%2Fid/typing');
     });
 
+    it('encodes the delta cursor and folded typing request into the message query', async () => {
+        (apiClient.get as jest.Mock).mockResolvedValue({ messages: [], removed_ids: [], server_time: 'now', complete: false });
+
+        await chatApi.listMessages('match1', { typing: true });
+        await chatApi.listMessages('match1', { since: '2026-08-27T12:00:00.000+01:00' });
+        await chatApi.listMessages('match1', { since: '2026-08-27T12:00:00.000Z', typing: true });
+
+        expect(apiClient.get).toHaveBeenNthCalledWith(1, '/v1/matches/match1/messages?typing=true');
+        expect(apiClient.get).toHaveBeenNthCalledWith(2, '/v1/matches/match1/messages?since=2026-08-27T12%3A00%3A00.000%2B01%3A00');
+        expect(apiClient.get).toHaveBeenNthCalledWith(3, '/v1/matches/match1/messages?since=2026-08-27T12%3A00%3A00.000Z&typing=true');
+    });
+
     it('uses authenticated unread, receipt, deletion and reporting routes', async () => {
         (apiClient.get as jest.Mock).mockResolvedValue({ total: 0, by_match: {} });
         (apiClient.post as jest.Mock).mockResolvedValue({});