feat: backend project setup with FastAPI structure and dependencies

- Create directory structure per IMPLEMENTATION_PLAN.md Section 12
- Add requirements.txt with FastAPI, SQLAlchemy, CrewAI, etc.
- Add core/config.py for environment variable configuration
- Add core/database.py for SQLite connection
- Add core/security.py for password hashing and JWT
- Add FastAPI app entry point (main.py) with all API routers
- Add Uvicorn runner (run.py)
- Add API route stubs (auth, bots, backtest, simulate, config)
- Add db/models.py with SQLAlchemy models
- Add db/schemas.py with Pydantic schemas
- Add service stubs (ai_agent, backtest, simulate engines)
- Add .env.example with all required environment variables
- Verify server starts correctly

src/backend/app/main.py

@@ -0,0 +1,33 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from .api import auth, bots, backtest, simulate, config
+
+app = FastAPI(
+    title="Randebu Trading Bot API",
+    description="AI-powered trading bot platform API",
+    version="0.1.0",
+)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+app.include_router(auth.router, prefix="/api/auth", tags=["auth"])
+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.get("/")
+def root():
+    return {"status": "ok", "message": "Randebu Trading Bot API"}
+
+
+@app.get("/health")
+def health():
+    return {"status": "healthy"}