feat: add ManualDNSChallenge component and related hooks for manual DNS challenge management

- Implemented `useManualChallenge`, `useChallengePoll`, and `useManualChallengeMutations` hooks for managing manual DNS challenges.
- Created tests for the `useManualChallenge` hooks to ensure correct fetching and mutation behavior.
- Added `ManualDNSChallenge` component for displaying challenge details and actions.
- Developed end-to-end tests for the Manual DNS Provider feature, covering provider selection, challenge UI, and accessibility compliance.
- Included error handling tests for verification failures and network errors.

backend/internal/api/handlers/proxy_host_handler_test.go

@@ -397,7 +397,7 @@ func TestProxyHostConnection(t *testing.T) {
 	// Start a local listener
 	l, err := net.Listen("tcp", "127.0.0.1:0")
 	require.NoError(t, err)
-	defer l.Close()
+	defer func() { _ = l.Close() }()
 
 	addr := l.Addr().(*net.TCPAddr)