User api key: JSON rate limiting message & status code (#87)

* feat(auth): Implement API key authentication

This commit enables API access with an API key system. This change provides a better experience for programmatic access and third-party integrations.

Key changes include:
- **API Key Management:** Users can now generate, manage, and revoke persistent API keys through a new "API Keys" section in the settings UI.
- **Authentication Middleware:** API requests are now authenticated via an `X-API-KEY` header instead of the previous `Authorization: Bearer` token.
- **Backend Implementation:** Adds a new `api_keys` database table, along with corresponding services, controllers, and routes to manage the key lifecycle securely.
- **Rate Limiting:** The API rate limiter now uses the API key to identify and track requests.
- **Documentation:** The API authentication documentation has been updated to reflect the new method.

* Add configurable API rate limiting

Two new variables are added to `.env.example`:
- `RATE_LIMIT_WINDOW_MS`: The time window in milliseconds for which requests are checked (defaults to 15 minutes).
- `RATE_LIMIT_MAX_REQUESTS`: The maximum number of requests allowed from an IP within the window (defaults to 100).

The installation documentation has been updated to reflect these new configuration options.

* Disable API operation in demo mode

* Exclude public API endpoints from rate limiting

* JSON rate limiting message & status code

---------

Co-authored-by: Wayne <5291640+ringoinca@users.noreply.github.com>

packages/backend/src/api/middleware/rateLimiter.ts

@@ -6,7 +6,11 @@ const windowInMinutes = Math.ceil(config.api.rateLimit.windowMs / 60000);
 export const rateLimiter = rateLimit({
 	windowMs: config.api.rateLimit.windowMs,
 	max: config.api.rateLimit.max,
-	message: `Too many requests from this IP, please try again after ${windowInMinutes} minutes`,
+	message: {
+		status: 429,
+		message: `Too many requests from this IP, please try again after ${windowInMinutes} minutes`
+	},
+	statusCode: 429,
 	standardHeaders: true,
-	legacyHeaders: false,
+	legacyHeaders: false
 });