feat(backend): Implement AVE Cloud integration for Data and Trading APIs

- Add tier field to User model for plan detection (free/normal/pro)
- Create AVE Cloud API client with all Data API endpoints:
  - Token search (GET /v2/tokens)
  - Batch prices (POST /v2/tokens/price)
  - Token details (GET /v2/tokens/{id})
  - Kline data (GET /v2/klines/token/{id})
  - Trending tokens (GET /v2/tokens/trending)
  - Token risk (GET /v2/contracts/{id})
- Add Trading API endpoints:
  - Chain wallet quote (POST /v1/chain/quote)
  - Chain wallet swap (POST /v1/chain/swap)
- Add tier gating with upsell messaging for Pro features
- Handle rate limiting gracefully with 429 responses
- Add Pydantic schemas for AVE API requests/responses

Fixes #11

src/backend/app/main.py

@@ -2,7 +2,7 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from slowapi import Limiter
 from slowapi.util import get_remote_address
-from .api import auth, bots, backtest, simulate, config
+from .api import auth, bots, backtest, simulate, config, ave
 from .core.limiter import limiter
 
 app = FastAPI(
@@ -26,6 +26,7 @@ app.include_router(bots.router, prefix="/api/bots", tags=["bots"])
 app.include_router(backtest.router, prefix="/api", tags=["backtest"])
 app.include_router(simulate.router, prefix="/api", tags=["simulate"])
 app.include_router(config.router, prefix="/api/config", tags=["config"])
+app.include_router(ave.router, prefix="/api/ave", tags=["ave"])
 
 
 @app.get("/")