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/frontend/package-lock.json

@@ -14,6 +14,7 @@
         "react": "^19.1.1",
         "react-dom": "^19.1.1",
         "react-hook-form": "^7.62.0",
+        "react-hot-toast": "^2.6.0",
         "react-router-dom": "^7.8.2",
         "zod": "^4.1.5",
         "zustand": "^5.0.8"
@@ -2152,7 +2153,6 @@
       "version": "3.1.3",
       "resolved": "https://registry.npmjs.org/csstype/-/csstype-3.1.3.tgz",
       "integrity": "sha512-M1uQkMl8rQK/szD0LNhtqxIPLpimGm8sOBwU7lLnCpSbTyY3yeU1Vc7l4KT5zT4s/yOxHH5O7tIuuLOCnLADRw==",
-      "devOptional": true,
       "license": "MIT"
     },
     "node_modules/debug": {
@@ -2770,6 +2770,15 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/goober": {
+      "version": "2.1.16",
+      "resolved": "https://registry.npmjs.org/goober/-/goober-2.1.16.tgz",
+      "integrity": "sha512-erjk19y1U33+XAMe1VTvIONHYoSqE4iS7BYUZfHaqeohLmnC0FdxEh7rQU+6MZ4OajItzjZFSRtVANrQwNq6/g==",
+      "license": "MIT",
+      "peerDependencies": {
+        "csstype": "^3.0.10"
+      }
+    },
     "node_modules/gopd": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/gopd/-/gopd-1.2.0.tgz",
@@ -3389,6 +3398,23 @@
         "react": "^16.8.0 || ^17 || ^18 || ^19"
       }
     },
+    "node_modules/react-hot-toast": {
+      "version": "2.6.0",
+      "resolved": "https://registry.npmjs.org/react-hot-toast/-/react-hot-toast-2.6.0.tgz",
+      "integrity": "sha512-bH+2EBMZ4sdyou/DPrfgIouFpcRLCJ+HoCA32UoAYHn6T3Ur5yfcDCeSr5mwldl6pFOsiocmrXMuoCJ1vV8bWg==",
+      "license": "MIT",
+      "dependencies": {
+        "csstype": "^3.1.3",
+        "goober": "^2.1.16"
+      },
+      "engines": {
+        "node": ">=10"
+      },
+      "peerDependencies": {
+        "react": ">=16",
+        "react-dom": ">=16"
+      }
+    },
     "node_modules/react-refresh": {
       "version": "0.17.0",
       "resolved": "https://registry.npmjs.org/react-refresh/-/react-refresh-0.17.0.tgz",