feat(webui): remove affordance for custom registries (MCP-1064) #1673

Job	Run time
Build Frontend	23s
Cross-Platform Logging Tests (macos-latest, $HOME/Library/Logs/mcpproxy, macOS File System Progra...	1m 40s
Cross-Platform Logging Tests (windows-latest, $env:LOCALAPPDATA\mcpproxy\logs, Windows Applicatio...	3m 1s
Cross-Platform Logging Tests (ubuntu-latest)	1m 51s
OAuth E2E Tests	50s
End-to-End Tests (ubuntu-latest, 1.25)	9m 47s
Integration Tests	5m 1s
Stress Tests	0s
	22m 33s

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