Add OAuth 2.0 authentication support for Jira Data Center

- Add OAuth 2.0 configuration options in backend env.ts
- Create authService.ts for OAuth flow, token management, and sessions
- Create auth.ts routes for login, callback, logout, and user info
- Update JiraAssets service to use user tokens when OAuth is enabled
- Add cookie-parser for session handling
- Create Login.tsx component with Jira OAuth login button
- Add authStore.ts (Zustand) for frontend auth state management
- Update App.tsx to show login page when OAuth is enabled
- Add user menu with logout functionality
- Document OAuth setup in CLAUDE.md

Supports two modes:
1. Service Account: Uses JIRA_PAT for all requests (default)
2. OAuth 2.0: Each user authenticates with their Jira credentials

backend/package.json

@@ -11,6 +11,7 @@
   "dependencies": {
     "@anthropic-ai/sdk": "^0.32.1",
     "better-sqlite3": "^11.6.0",
+    "cookie-parser": "^1.4.7",
     "cors": "^2.8.5",
     "dotenv": "^16.4.5",
     "express": "^4.21.1",
@@ -22,6 +23,7 @@
   },
   "devDependencies": {
     "@types/better-sqlite3": "^7.6.12",
+    "@types/cookie-parser": "^1.4.10",
     "@types/cors": "^2.8.17",
     "@types/express": "^5.0.0",
     "@types/node": "^22.9.0",