feat: 전문적이고 모던한 OAuth 로그인 UI 구현

- AiMond Authorization 브랜딩 적용
- 다크모드 기반 글래스모피즘 디자인
- 애니메이션 효과 (플로팅, 그라디언트, 포커스)
- React Router 기반 라우팅 구조
- AuthContext를 통한 인증 상태 관리
- 대시보드 및 관리 페이지 기본 구조
- Backend API 엔드포인트 구조 개선
- pymongo 호환성 문제 수정

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

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

oauth/backend/app/core/security.py

@@ -0,0 +1,51 @@
+from datetime import datetime, timedelta
+from typing import Optional, Dict, Any
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/v1/auth/login")
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    return pwd_context.verify(plain_password, hashed_password)
+
+def get_password_hash(password: str) -> str:
+    return pwd_context.hash(password)
+
+def create_access_token(data: Dict[str, Any], expires_delta: Optional[timedelta] = None) -> str:
+    to_encode = data.copy()
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    to_encode.update({"exp": expire})
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    return encoded_jwt
+
+async def get_current_user(token: str = Depends(oauth2_scheme)):
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    try:
+        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
+        username: str = payload.get("sub")
+        if username is None:
+            raise credentials_exception
+    except JWTError:
+        raise credentials_exception
+    
+    # TODO: Get user from database
+    return {"email": username, "role": "user"}
+
+async def require_admin(current_user = Depends(get_current_user)):
+    if current_user.get("role") != "system_admin":
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Not enough permissions"
+        )
+    return current_user