fix(auth): Improve OAuth credential detection and startup warning

- Enhanced getClaudeAuthIndicators() to return detailed check information
  including file paths checked and specific error details for debugging
- Added debug logging to server startup credential detection for easier
  troubleshooting in Docker environments
- Show paths that were checked in the warning message to help users debug
  mount issues
- Added support for CLAUDE_CODE_OAUTH_TOKEN environment variable
- Return authType in verify-claude-auth response to distinguish between
  OAuth and CLI authentication methods
- Updated UI to show specific success messages for Claude Code subscription
  vs generic CLI auth
- Added Docker troubleshooting tips to sandbox risk dialog
- Added comprehensive unit tests for OAuth credential detection scenarios

Closes #721

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ui/src/lib/http-api-client.ts

@@ -1350,6 +1350,7 @@ export class HttpApiClient implements ElectronAPI {
     ): Promise<{
       success: boolean;
       authenticated: boolean;
+      authType?: 'oauth' | 'api_key' | 'cli';
       error?: string;
     }> => this.post('/api/setup/verify-claude-auth', { authMethod, apiKey }),