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/db/models.py

@@ -0,0 +1,121 @@
+import uuid
+from datetime import datetime
+from sqlalchemy import (
+    Column,
+    String,
+    Text,
+    Float,
+    Boolean,
+    DateTime,
+    ForeignKey,
+    Index,
+    JSON,
+)
+from sqlalchemy.orm import relationship
+from ..core.database import Base
+
+
+def generate_uuid():
+    return str(uuid.uuid4())
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    id = Column(String, primary_key=True, default=generate_uuid)
+    email = Column(String, unique=True, nullable=False)
+    password_hash = Column(String, nullable=False)
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    bots = relationship("Bot", back_populates="user", cascade="all, delete-orphan")
+
+
+class Bot(Base):
+    __tablename__ = "bots"
+
+    id = Column(String, primary_key=True, default=generate_uuid)
+    user_id = Column(String, ForeignKey("users.id"), nullable=False)
+    name = Column(String, nullable=False)
+    description = Column(Text)
+    strategy_config = Column(JSON, nullable=False)
+    llm_config = Column(JSON, nullable=False)
+    status = Column(String, default="draft")
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    user = relationship("User", back_populates="bots")
+    conversations = relationship(
+        "BotConversation", back_populates="bot", cascade="all, delete-orphan"
+    )
+    backtests = relationship(
+        "Backtest", back_populates="bot", cascade="all, delete-orphan"
+    )
+    simulations = relationship(
+        "Simulation", back_populates="bot", cascade="all, delete-orphan"
+    )
+    signals = relationship("Signal", back_populates="bot", cascade="all, delete-orphan")
+
+
+class BotConversation(Base):
+    __tablename__ = "bot_conversations"
+
+    id = Column(String, primary_key=True, default=generate_uuid)
+    bot_id = Column(String, ForeignKey("bots.id"), nullable=False)
+    role = Column(String, nullable=False)
+    content = Column(Text, nullable=False)
+    created_at = Column(DateTime, default=datetime.utcnow)
+
+    bot = relationship("Bot", back_populates="conversations")
+
+
+class Backtest(Base):
+    __tablename__ = "backtests"
+
+    id = Column(String, primary_key=True, default=generate_uuid)
+    bot_id = Column(String, ForeignKey("bots.id"), nullable=False)
+    started_at = Column(DateTime, nullable=False)
+    ended_at = Column(DateTime)
+    status = Column(String, nullable=False)
+    config = Column(JSON, nullable=False)
+    result = Column(JSON)
+
+    bot = relationship("Bot", back_populates="backtests")
+
+
+class Simulation(Base):
+    __tablename__ = "simulations"
+
+    id = Column(String, primary_key=True, default=generate_uuid)
+    bot_id = Column(String, ForeignKey("bots.id"), nullable=False)
+    started_at = Column(DateTime, nullable=False)
+    status = Column(String, nullable=False)
+    config = Column(JSON, nullable=False)
+    signals = Column(JSON)
+
+    bot = relationship("Bot", back_populates="simulations")
+
+
+class Signal(Base):
+    __tablename__ = "signals"
+
+    id = Column(String, primary_key=True, default=generate_uuid)
+    bot_id = Column(String, ForeignKey("bots.id"), nullable=False)
+    run_id = Column(String, nullable=False)
+    signal_type = Column(String, nullable=False)
+    token = Column(String, nullable=False)
+    price = Column(Float, nullable=False)
+    confidence = Column(Float)
+    reasoning = Column(Text)
+    executed = Column(Boolean, default=False)
+    created_at = Column(DateTime, default=datetime.utcnow)
+
+    bot = relationship("Bot", back_populates="signals")
+
+
+Index("idx_bots_user_id", Bot.user_id)
+Index("idx_conversations_bot_id", BotConversation.bot_id)
+Index("idx_backtests_bot_id", Backtest.bot_id)
+Index("idx_simulations_bot_id", Simulation.bot_id)
+Index("idx_signals_bot_id", Signal.bot_id)
+Index("idx_signals_run_id", Signal.run_id)