Add CORS support and response caching to aggregate endpoints

- Introduced CORS configuration options in config.example.yaml, allowing specification of allowed origins for cross-origin requests.
- Enhanced the aggregate handler to support response caching with a configurable TTL, improving performance for repeated requests.
- Updated the aggregate API to return a structured response indicating whether any upstream requests failed, enhancing error handling and response clarity.
- Modified documentation in AGGREGATE.md and README.md to reflect the new CORS and caching features.
- Added tests to validate the new functionality in the aggregate handler.

README.md

@@ -55,7 +55,8 @@ docker compose logs -f gateway
 |----------|------------|
 | **[docs/GATEWAY_RUN.md](docs/GATEWAY_RUN.md)** | Полная инструкция: конфиг, pull/registry, Docker CLI, Compose, CI/CD, неполадки |
 | **[docs/API.md](docs/API.md)** | Контракт Telemt Control API (`/v1/…`) |
-| **[docs/AGGREGATE.md](docs/AGGREGATE.md)** | Агрегирующие эндпоинты шлюза (`/api/agg/…`) |
+| **[docs/AGGREGATE.md](docs/AGGREGATE.md)** | Агрегирующие эндпоинты шлюза (`/api/agg/…`), CORS, кэш |
+| **[docs/AGGREGATE_OPENAPI.yaml](docs/AGGREGATE_OPENAPI.yaml)** | OpenAPI 3 черновик для `/api/agg/*` (генерация типов для UI) |
 | **[docs/GEOIP.md](docs/GEOIP.md)** | GeoLite2 City (страна/город) и опционально ASN (номер AS, организация) для IP в `unique-ips` |
 
 ## Сборка и тесты без Docker