feat: implement GraphQL member management API

Implement complete member management system with GraphQL API per OpenSpec proposal.
Only firstName is required; all other fields are optional with conditional validation.

Key features:
- GraphQL CRUD operations (create, read, update, delete members)
- SQLAlchemy 2.0 async with SQLite database
- Alembic database migrations
- Conditional validation (email/phone validated only when provided)
- Member fields: firstName (required), lastName, address, email, phone (all optional)
- Database seed script with sample member
- FastAPI with Strawberry GraphQL integration

Implementation details:
- Python 3.11+ with uv package manager
- Async database sessions throughout
- Proper error handling and validation
- Code quality: black, isort, ruff
- Comprehensive end-to-end testing completed

All 20 tasks from OpenSpec proposal completed successfully.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/database.py

@@ -0,0 +1,39 @@
+from typing import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from src.config import settings
+
+# Create async engine
+async_engine = create_async_engine(
+    settings.database_url,
+    echo=settings.debug,
+    future=True,
+)
+
+# Create async session factory
+async_session_maker = async_sessionmaker(
+    async_engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+)
+
+
+# Declarative base for models
+class Base(DeclarativeBase):
+    pass
+
+
+# Dependency for FastAPI
+async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
+    """Provide database session for FastAPI dependency injection."""
+    async with async_session_maker() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise
+        finally:
+            await session.close()