Migrate frontend to shadcn/ui + add Gitea branch panel in endpoint editor

shadcn/ui migration:
- Installed shadcn components: Button, Input, Label, Card, Badge, Checkbox,
  Switch, Tabs, Dialog, Select, Tooltip, Toaster (sonner)
- Migrated all pages: Login, Dashboard, Settings, Endpoints, EndpointEditor,
  Folders, ApiKeys, Logs
- Replaced react-hot-toast with sonner
- Added CSS variables for theming
- Updated tailwind.config.js for shadcn

Gitea branch panel in EndpointEditor:
- GiteaBranchPanel component: branch selector, save to branch, compare
  with main, create PR, merge, commit history
- New backend endpoints: getEndpointFileContent, commitEndpoint,
  getEndpointCommits, getEndpointFromBranch, commitEndpointToBranch
- Frontend giteaApi: extended with endpoint-specific methods

Fixes:
- Fixed sync-all PostgreSQL-compatible UPDATE LIMIT
- .gitignore: added tmp/

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -17,21 +17,38 @@
     "@dagrejs/dagre": "^1.1.8",
     "@hookform/resolvers": "^3.3.3",
     "@monaco-editor/react": "^4.6.0",
+    "@radix-ui/react-alert-dialog": "^1.1.15",
+    "@radix-ui/react-checkbox": "^1.3.3",
+    "@radix-ui/react-collapsible": "^1.1.12",
+    "@radix-ui/react-dialog": "^1.1.15",
+    "@radix-ui/react-dropdown-menu": "^2.1.16",
+    "@radix-ui/react-label": "^2.1.8",
+    "@radix-ui/react-scroll-area": "^1.2.10",
+    "@radix-ui/react-select": "^2.2.6",
+    "@radix-ui/react-separator": "^1.1.8",
+    "@radix-ui/react-slot": "^1.2.4",
+    "@radix-ui/react-switch": "^1.2.6",
+    "@radix-ui/react-tabs": "^1.1.13",
+    "@radix-ui/react-tooltip": "^1.2.8",
     "@tanstack/react-query": "^5.14.2",
     "@xyflow/react": "^12.10.0",
     "axios": "^1.6.2",
+    "class-variance-authority": "^0.7.1",
     "clsx": "^2.0.0",
     "cmdk": "^0.2.0",
     "date-fns": "^3.0.6",
     "framer-motion": "^10.16.16",
     "lucide-react": "^0.303.0",
+    "next-themes": "^0.4.6",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
     "react-hook-form": "^7.49.2",
     "react-hot-toast": "^2.4.1",
     "react-icons": "^4.12.0",
     "react-router-dom": "^6.20.1",
+    "sonner": "^2.0.7",
     "tailwind-merge": "^2.2.0",
+    "tailwindcss-animate": "^1.0.7",
     "zod": "^3.22.4",
     "zustand": "^4.4.7"
   },