[UI-6] Create OAuthDebuggerModal component #8

Labels: v2, enhancement
Files: client/src/components/OAuthDebuggerModal.tsx (NEW)

Step-by-step OAuth flow visualization for debugging authentication issues.

Tasks

• Step 1: Authorization Request - Display URL with all parameters
• Step 2: Authorization Code - Show code received and state verification
• Step 3: Token Exchange - Show request/response
• Step 4: Access Token - Display token with expiration
• Refresh Token section with "Test Refresh Now" button
• JWT decode display (header and payload)
• Actions: Test Refresh, Revoke Token, Start New Flow, Copy

Spec Reference

v2_ux.md - "OAuth Debugger"