fix(gateway): 전용 데이터베이스 URL을 우선 사용한다

릴리스 프로세스가 전달한 GATEWAY_DATABASE_URL을 API와 orchestrator가 직접 사용하도록 고친다. 원시 POSTGRES_* 재조합으로 특수문자 비밀번호가 깨지는 회귀를 테스트한다.

app/gateway-api/test/gatewayPostgresConfig.test.ts

@@ -0,0 +1,33 @@
+import { describe, expect, it } from 'vitest';
+
+import { resolveGatewayPostgresConfigFromEnv } from '../src/gatewayPostgresConfig.js';
+
+describe('resolveGatewayPostgresConfigFromEnv', () => {
+    it('uses the encoded Gateway URL instead of rebuilding one from raw PostgreSQL credentials', () => {
+        const config = resolveGatewayPostgresConfigFromEnv(
+            {
+                GATEWAY_DATABASE_URL: 'postgresql://sammo:encoded%23password@postgres:5432/sammo?schema=legacy',
+                POSTGRES_USER: 'sammo',
+                POSTGRES_PASSWORD: 'raw#password',
+                POSTGRES_HOST: 'postgres',
+                POSTGRES_PORT: '5432',
+                POSTGRES_DB: 'sammo',
+                POSTGRES_POOL_MAX: '4',
+            },
+            'public'
+        );
+
+        const parsed = new URL(config.url);
+        expect(parsed.password).toBe('encoded%23password');
+        expect(parsed.searchParams.get('schema')).toBe('public');
+        expect(config.maxConnections).toBe(4);
+    });
+
+    it('keeps DATABASE_URL as the fallback for existing launchers', () => {
+        const config = resolveGatewayPostgresConfigFromEnv({
+            DATABASE_URL: 'postgresql://sammo:password@postgres:5432/sammo?schema=public',
+        });
+
+        expect(config.url).toBe('postgresql://sammo:password@postgres:5432/sammo?schema=public');
+    });
+});