feat: add all application source code

- apps/api: FastAPI backend with Dockerfile
- apps/web: Next.js frontend with Dockerfile
- apps/sensor: Signal collection agent
- packages: shared packages

Co-Authored-By: Claude <noreply@anthropic.com>

apps/api/src/db/base.py

@@ -0,0 +1,141 @@
+"""
+Database Base Configuration
+===========================
+CTO-201: Async SQLAlchemy setup
+
+Features:
+- SQLAlchemy 2.0 async engine
+- aiosqlite for local dev
+- PostgreSQL-ready (asyncpg)
+- Session dependency injection
+"""
+
+from collections.abc import AsyncGenerator
+from contextlib import asynccontextmanager
+
+from sqlalchemy.ext.asyncio import (
+    AsyncEngine,
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+from sqlalchemy.orm import DeclarativeBase
+
+from src.core.config import settings
+
+
+# =============================================================================
+# Base Model
+# =============================================================================
+
+class Base(DeclarativeBase):
+    """SQLAlchemy declarative base"""
+    pass
+
+
+# =============================================================================
+# Engine & Session Factory
+# =============================================================================
+
+_engine: AsyncEngine | None = None
+_session_factory: async_sessionmaker[AsyncSession] | None = None
+
+
+def get_engine() -> AsyncEngine:
+    """Get or create async engine"""
+    global _engine
+    if _engine is None:
+        # SQLite 需要特殊處理
+        connect_args = {}
+        if settings.SQLITE_DATABASE_URL.startswith("sqlite"):
+            connect_args["check_same_thread"] = False
+
+        _engine = create_async_engine(
+            settings.SQLITE_DATABASE_URL,
+            echo=settings.DEBUG,
+            connect_args=connect_args,
+        )
+    return _engine
+
+
+def get_session_factory() -> async_sessionmaker[AsyncSession]:
+    """Get or create session factory"""
+    global _session_factory
+    if _session_factory is None:
+        _session_factory = async_sessionmaker(
+            bind=get_engine(),
+            class_=AsyncSession,
+            expire_on_commit=False,
+            autoflush=False,
+        )
+    return _session_factory
+
+
+# =============================================================================
+# Dependency Injection
+# =============================================================================
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """
+    FastAPI dependency for database session
+
+    Usage:
+        @router.get("/items")
+        async def get_items(db: AsyncSession = Depends(get_db)):
+            ...
+    """
+    factory = get_session_factory()
+    async with factory() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise
+
+
+@asynccontextmanager
+async def get_db_context() -> AsyncGenerator[AsyncSession, None]:
+    """
+    Context manager for database session (non-FastAPI usage)
+
+    Usage:
+        async with get_db_context() as db:
+            ...
+    """
+    factory = get_session_factory()
+    async with factory() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise
+
+
+# =============================================================================
+# Initialization
+# =============================================================================
+
+async def init_db() -> None:
+    """
+    Initialize database tables
+
+    Call this at application startup.
+    """
+    engine = get_engine()
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+
+async def close_db() -> None:
+    """
+    Close database connections
+
+    Call this at application shutdown.
+    """
+    global _engine, _session_factory
+    if _engine is not None:
+        await _engine.dispose()
+        _engine = None
+        _session_factory = None