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/api/src/domains/profile-settings/repository.ts

@@ -1,5 +1,6 @@
 import { randomUUID } from 'node:crypto';
 import { Pool, type QueryResultRow } from 'pg';
+import { closeResolvedPool, resolvePool, type DatabaseConnection } from '../../db/pool.js';
 import type {
   FeedbackSubmission,
   NotificationPreferenceKey,
@@ -80,9 +81,12 @@ function assertChanged(rowCount: number | null): void {
 
 export class PostgresProfileSettingsRepository implements ProfileSettingsRepository {
   private readonly pool: Pool;
+  private readonly ownsPool: boolean;
 
-  constructor(databaseUrl: string) {
-    this.pool = new Pool({ connectionString: databaseUrl });
+  constructor(connection: DatabaseConnection) {
+    const resolved = resolvePool(connection);
+    this.pool = resolved.pool;
+    this.ownsPool = resolved.owned;
   }
 
   async updateProfile(userId: string, update: ProfileUpdate): Promise<void> {
@@ -146,6 +150,6 @@ export class PostgresProfileSettingsRepository implements ProfileSettingsReposit
   }
 
   async close(): Promise<void> {
-    await this.pool.end();
+    await closeResolvedPool(this.pool, this.ownsPool);
   }
 }