Fix Worker hang: use per-request connections instead of cached pool

The module-level cached mysql2 pool could hold stale connections when
the Worker isolate went idle, causing the next request to hang forever.

Switch from createPool (cached) to createConnection (per-request) with
proper cleanup via connection.end() in a finally block. Hyperdrive
handles actual connection pooling at the edge, so mysql2 pooling is
unnecessary and harmful. Also adds connectTimeout: 5000 as a safety net.

https://claude.ai/code/session_01K4SCzhd53zgSyEEoNPF59B

Author: claude

src/db/index.ts

@@ -1,31 +1,25 @@
 import { getCloudflareContext } from "@opennextjs/cloudflare";
 import { drizzle, type MySql2Database } from "drizzle-orm/mysql2";
-import { createPool } from "mysql2/promise";
+import { createConnection } from "mysql2/promise";
 import * as schema from "./schema";
 
 export type Db = MySql2Database<typeof schema>;
 
-let _db: Db | undefined;
-
-export function getDb(): Db {
-	if (_db) return _db;
-
-	const { env } = getCloudflareContext();
-	_db = drizzle(
-		createPool({
-			host: env.HYPERDRIVE.host,
-			user: env.HYPERDRIVE.user,
-			password: env.HYPERDRIVE.password,
-			database: env.HYPERDRIVE.database,
-			port: env.HYPERDRIVE.port,
-			disableEval: true,
-			connectionLimit: 1,
-		}),
-		{ schema, mode: "default" },
-	);
-	return _db;
-}
-
 export async function withDb<T>(callback: (db: Db) => Promise<T>): Promise<T> {
-	return callback(getDb());
+	const { env } = getCloudflareContext();
+	const connection = await createConnection({
+		host: env.HYPERDRIVE.host,
+		user: env.HYPERDRIVE.user,
+		password: env.HYPERDRIVE.password,
+		database: env.HYPERDRIVE.database,
+		port: env.HYPERDRIVE.port,
+		disableEval: true,
+		connectTimeout: 5000,
+	});
+	const db = drizzle(connection, { schema, mode: "default" });
+	try {
+		return await callback(db);
+	} finally {
+		await connection.end();
+	}
 }