feat: scaffold v2 project structure with Docker, FastAPI, and config

동작하는 최소 코드 수준의 v2 스캐폴딩:

- docker-compose.yml: postgres, fastapi, kordoc, frontend, caddy
- app/: FastAPI 백엔드 (main, core, models, ai, prompts)
- services/kordoc/: Node.js 문서 파싱 마이크로서비스
- gpu-server/: AI Gateway + GPU docker-compose
- frontend/: SvelteKit 기본 구조
- migrations/: PostgreSQL 초기 스키마 (documents, tasks, processing_queue)
- tests/: pytest conftest 기본 설정
- config.yaml, Caddyfile, credentials.env.example 갱신

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/core/database.py

@@ -0,0 +1,34 @@
+"""PostgreSQL 연결 — SQLAlchemy async engine + session factory"""
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from core.config import settings
+
+engine = create_async_engine(
+    settings.database_url,
+    echo=False,
+    pool_size=10,
+    max_overflow=20,
+)
+
+async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def init_db():
+    """DB 연결 확인 (스키마는 migrations/로 관리)"""
+    async with engine.begin() as conn:
+        # 연결 테스트
+        await conn.execute(
+            __import__("sqlalchemy").text("SELECT 1")
+        )
+
+
+async def get_session() -> AsyncSession:
+    """FastAPI Depends용 세션 제공"""
+    async with async_session() as session:
+        yield session