Initial commit: Backend API Phase 1a complete

- FastAPI backend with JWT auth
- PostgreSQL database schema
- Trees and Sessions CRUD APIs
- Export functionality (Markdown, Text, HTML)
- Docker setup for local development
- Alembic migrations

backend/app/core/__init__.py

@@ -0,0 +1 @@
+# Core module

backend/app/core/config.py

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+from pydantic_settings import BaseSettings
+from typing import Optional
+
+
+class Settings(BaseSettings):
+    # Application
+    APP_NAME: str = "Troubleshooting Decision Tree"
+    DEBUG: bool = False
+    API_V1_PREFIX: str = "/api/v1"
+
+    # Database
+    DATABASE_URL: str = "postgresql+asyncpg://postgres:postgres@localhost:5432/decision_tree"
+    DATABASE_URL_SYNC: str = "postgresql://postgres:postgres@localhost:5432/decision_tree"
+
+    # JWT Settings
+    SECRET_KEY: str = "your-secret-key-change-in-production-use-openssl-rand-hex-32"
+    ALGORITHM: str = "HS256"
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 15
+    REFRESH_TOKEN_EXPIRE_DAYS: int = 7
+
+    # Security
+    BCRYPT_ROUNDS: int = 12
+
+    # CORS
+    CORS_ORIGINS: list[str] = ["http://localhost:3000", "http://localhost:5173"]
+
+    class Config:
+        env_file = ".env"
+        case_sensitive = True
+
+
+settings = Settings()

backend/app/core/database.py

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+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+from .config import settings
+
+# Create async engine
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=settings.DEBUG,
+    future=True
+)
+
+# Create async session factory
+async_session_maker = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False
+)
+
+
+class Base(DeclarativeBase):
+    """Base class for all database models."""
+    pass
+
+
+async def get_db() -> AsyncSession:
+    """Dependency to get database session."""
+    async with async_session_maker() as session:
+        try:
+            yield session
+        finally:
+            await session.close()
+
+
+async def init_db():
+    """Initialize database tables."""
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)

backend/app/core/security.py

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+from datetime import datetime, timedelta, timezone
+from typing import Optional
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+from .config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    """Verify a password against its hash."""
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_password_hash(password: str) -> str:
+    """Hash a password."""
+    return pwd_context.hash(password, rounds=settings.BCRYPT_ROUNDS)
+
+
+def create_access_token(data: dict, expires_delta: Optional[timedelta] = None) -> str:
+    """Create a JWT access token."""
+    to_encode = data.copy()
+    if expires_delta:
+        expire = datetime.now(timezone.utc) + expires_delta
+    else:
+        expire = datetime.now(timezone.utc) + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    to_encode.update({"exp": expire, "type": "access"})
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    return encoded_jwt
+
+
+def create_refresh_token(data: dict) -> str:
+    """Create a JWT refresh token."""
+    to_encode = data.copy()
+    expire = datetime.now(timezone.utc) + timedelta(days=settings.REFRESH_TOKEN_EXPIRE_DAYS)
+    to_encode.update({"exp": expire, "type": "refresh"})
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    return encoded_jwt
+
+
+def decode_token(token: str) -> Optional[dict]:
+    """Decode and validate a JWT token."""
+    try:
+        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
+        return payload
+    except JWTError:
+        return None