🎉 Initial commit: Document Server MVP

✨ Features implemented:
- FastAPI backend with JWT authentication
- PostgreSQL database with async SQLAlchemy
- HTML document viewer with smart highlighting
- Note system connected to highlights (1:1 relationship)
- Bookmark system for quick navigation
- Integrated search (documents + notes)
- Tag system for document organization
- Docker containerization with Nginx

🔧 Technical stack:
- Backend: FastAPI + PostgreSQL + Redis
- Frontend: Alpine.js + Tailwind CSS
- Authentication: JWT tokens
- File handling: HTML + PDF support
- Search: Full-text search with relevance scoring

📋 Core functionality:
- Text selection → Highlight creation
- Highlight → Note attachment
- Note management with search/filtering
- Bookmark creation at scroll positions
- Document upload with metadata
- User management (admin creates accounts)

backend/src/core/database.py

@@ -0,0 +1,94 @@
+"""
+데이터베이스 설정 및 연결
+"""
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+from sqlalchemy import MetaData
+from typing import AsyncGenerator
+
+from src.core.config import settings
+
+
+# SQLAlchemy 메타데이터 설정
+metadata = MetaData(
+    naming_convention={
+        "ix": "ix_%(column_0_label)s",
+        "uq": "uq_%(table_name)s_%(column_0_name)s",
+        "ck": "ck_%(table_name)s_%(constraint_name)s",
+        "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
+        "pk": "pk_%(table_name)s"
+    }
+)
+
+
+class Base(DeclarativeBase):
+    """SQLAlchemy Base 클래스"""
+    metadata = metadata
+
+
+# 비동기 데이터베이스 엔진 생성
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=settings.DEBUG,
+    future=True,
+    pool_pre_ping=True,
+    pool_recycle=300,
+)
+
+# 비동기 세션 팩토리
+AsyncSessionLocal = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+)
+
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """데이터베이스 세션 의존성"""
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        except Exception:
+            await session.rollback()
+            raise
+        finally:
+            await session.close()
+
+
+async def init_db() -> None:
+    """데이터베이스 초기화"""
+    from src.models import user, document, highlight, note, bookmark, tag
+    
+    async with engine.begin() as conn:
+        # 모든 테이블 생성
+        await conn.run_sync(Base.metadata.create_all)
+    
+    # 관리자 계정 생성
+    await create_admin_user()
+
+
+async def create_admin_user() -> None:
+    """관리자 계정 생성 (존재하지 않을 경우)"""
+    from src.models.user import User
+    from src.core.security import get_password_hash
+    from sqlalchemy import select
+    
+    async with AsyncSessionLocal() as session:
+        # 관리자 계정 존재 확인
+        result = await session.execute(
+            select(User).where(User.email == settings.ADMIN_EMAIL)
+        )
+        admin_user = result.scalar_one_or_none()
+        
+        if not admin_user:
+            # 관리자 계정 생성
+            admin_user = User(
+                email=settings.ADMIN_EMAIL,
+                hashed_password=get_password_hash(settings.ADMIN_PASSWORD),
+                is_active=True,
+                is_admin=True,
+                full_name="Administrator"
+            )
+            session.add(admin_user)
+            await session.commit()
+            print(f"관리자 계정이 생성되었습니다: {settings.ADMIN_EMAIL}")