fix: add QueryResultRow constraint to db query generic

pg's Pool.query<T> requires T extends QueryResultRow. Added the
constraint and imported the type.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/db/client.ts

@@ -1,4 +1,4 @@
-import { Pool, PoolClient, QueryResult } from "pg";
+import { Pool, PoolClient, QueryResult, QueryResultRow } from "pg";
 
 // ─── Connection pool ──────────────────────────────────────────────────────────
 
@@ -26,7 +26,7 @@ function getPool(): Pool {
 
 // ─── Query helpers ────────────────────────────────────────────────────────────
 
-export async function query<T = Record<string, unknown>>(
+export async function query<T extends QueryResultRow = Record<string, unknown>>(
   text: string,
   params?: unknown[]
 ): Promise<QueryResult<T>> {