Add support for custom headers and migrate from legacy auth

- Introduced CustomHeaders component for managing custom headers.
- Updated Sidebar to include CustomHeaders component.
- Enhanced useConnection hook to handle custom headers and legacy auth migration.
- Added tests for custom headers functionality.
- Updated package.json and package-lock.json for new dependencies.

server/package.json

@@ -22,6 +22,7 @@
   "devDependencies": {
     "@types/cors": "^2.8.19",
     "@types/express": "^4.17.23",
+    "@types/shell-quote": "^1.7.5",
     "@types/ws": "^8.5.12",
     "tsx": "^4.19.0",
     "typescript": "^5.6.2"
@@ -30,6 +31,8 @@
     "@modelcontextprotocol/sdk": "^1.17.5",
     "cors": "^2.8.5",
     "express": "^5.1.0",
+    "shell-quote": "^1.8.3",
+    "spawn-rx": "^5.1.2",
     "ws": "^8.18.0",
     "zod": "^3.25.76"
   }