fix(deploy): migrate after stop and shrink DB pool

Stage migrate hit ER_CON_COUNT_ERROR while live still held the pool. Build in stage with DATABASE_POOL_SIZE=5, run db:migrate only after stopping the service (with retries), and lower the default pool from 40 to 10.

Co-authored-by: Cursor <[email protected]>

src/env.ts

@@ -8,7 +8,7 @@ const schema = z.object({
 		.enum(["development", "test", "production"])
 		.default("development"),
 	DATABASE_URL: z.string().url(),
-	DATABASE_POOL_SIZE: z.coerce.number().int().positive().default(40),
+	DATABASE_POOL_SIZE: z.coerce.number().int().positive().default(10),
 	DATABASE_IDLE_TIMEOUT_MS: z.coerce.number().int().positive().default(300_000),
 	DATABASE_CONNECT_TIMEOUT_MS: z.coerce
 		.number()