feat(Backend): update API gateway and websocket hubs

FinlyticBackend/Project.md

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+# Finlytic Backend Gateway
+
+Finlytic Backend is the central ASP.NET Core Web API gateway and SignalR real-time broker for the Finlytic ecosystem. It serves external clients (`FinlyticApp`, `FinlyticWeb`) via REST endpoints and WebSockets, while interfacing internally with background microservices strictly via MQTT.
+
+---
+
+## Architecture & Responsibilities
+
+1. **Single Public Entrypoint**:
+   - The **only** backend microservice hosting Kestrel HTTP REST and SignalR WebSocket endpoints.
+
+2. **JWT Authentication & User Management**:
+   - Manages user registration, login, JWT token issuance (`IJwtTokenService`), and role-based access control (Admin, Premium, User).
+
+3. **SignalR Real-Time Hubs**:
+   - **`NewsHub`** (`/hubs/news`): Broadcasts live news articles and sentiment classifications.
+   - **`TradeHub`** (`/hubs/trade-updates`): Broadcasts live trade proposals and position updates.
+   - **`TradeRealtimeHub`** (`/hubs/trades`): Legacy real-time trade signals hub.
+
+4. **MQTT Bridge (`BackendMqttBridge` & `WebMqttClient`)**:
+   - Subscribes to internal MQTT topics (`finlytic/news/#`, `finlytic/sentiment/#`, `finlytic/trades/#`, `finlytic/fundamentals/#`, `finlytic/ta/#`).
+   - Forwards MQTT messages to connected SignalR WebSockets and executes MQTT RPC requests for REST controllers.
+
+---
+
+## Feature Status
+
+### Implemented Features
+- [x] JWT Authentication & User Persistence (`BackendDbContext`).
+- [x] REST Controllers: `AuthController`, `NewsController`, `AssetsController`, `UserTradesController`, `UserFavoritesController`, `AdminController`.
+- [x] SignalR WebSockets for News & Trades (`NewsHub`, `TradeHub`).
+- [x] MQTT Bridge & RPC Gateway Client (`BackendMqttBridge`, `WebMqttClient`).
+- [x] Complete removal of mock data in REST responses.
+
+### Planned Features
+- [ ] OAuth2 / Social Login integration (Google / Apple Sign-In).
+- [ ] Two-Factor Authentication (2FA / TOTP).