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/services/ai_agent/__init__.py

@@ -0,0 +1,4 @@
+from .crew import CrewAgent
+from .llm_connector import LLMConnector
+
+__all__ = ["CrewAgent", "LLMConnector"]

src/backend/app/services/ai_agent/crew.py

@@ -0,0 +1,15 @@
+from typing import List, Optional
+
+
+class CrewAgent:
+    def __init__(self, role: str, goal: str, backstory: str):
+        self.role = role
+        self.goal = goal
+        self.backstory = backstory
+
+    def execute_task(self, task: str) -> str:
+        raise NotImplementedError("CrewAI agent not yet implemented")
+
+
+def get_trading_crew():
+    raise NotImplementedError("Trading crew not yet implemented")

src/backend/app/services/ai_agent/llm_connector.py

@@ -0,0 +1,13 @@
+from typing import Optional
+
+
+class LLMConnector:
+    def __init__(self, api_key: str, model: str = "MiniMax-Text-01"):
+        self.api_key = api_key
+        self.model = model
+
+    def chat(self, messages: list[dict], **kwargs):
+        raise NotImplementedError("LLM integration not yet implemented")
+
+    def parse_strategy(self, user_message: str) -> dict:
+        raise NotImplementedError("Strategy parsing not yet implemented")

src/backend/app/services/backtest/__init__.py

@@ -0,0 +1,3 @@
+from .engine import BacktestEngine
+
+__all__ = ["BacktestEngine"]

src/backend/app/services/backtest/engine.py

@@ -0,0 +1,15 @@
+from typing import Optional, Dict, Any
+
+
+class BacktestEngine:
+    def __init__(self, config: Dict[str, Any]):
+        self.config = config
+
+    async def run(self) -> Dict[str, Any]:
+        raise NotImplementedError("Backtest engine not yet implemented")
+
+    async def stop(self):
+        raise NotImplementedError("Backtest stop not yet implemented")
+
+    def get_results(self) -> Dict[str, Any]:
+        raise NotImplementedError("Backtest results not yet implemented")

src/backend/app/services/simulate/__init__.py

@@ -0,0 +1,3 @@
+from .engine import SimulateEngine
+
+__all__ = ["SimulateEngine"]

src/backend/app/services/simulate/engine.py

@@ -0,0 +1,15 @@
+from typing import Optional, Dict, Any, List
+
+
+class SimulateEngine:
+    def __init__(self, config: Dict[str, Any]):
+        self.config = config
+
+    async def run(self) -> List[Dict[str, Any]]:
+        raise NotImplementedError("Simulation engine not yet implemented")
+
+    async def stop(self):
+        raise NotImplementedError("Simulation stop not yet implemented")
+
+    def get_signals(self) -> List[Dict[str, Any]]:
+        raise NotImplementedError("Simulation signals not yet implemented")