feat: hide GitHub Copilot provider preset and auth tab

Users reported that Copilot support causes excessively fast token
consumption. Temporarily hide the feature by adding a `hidden` field
to ProviderPreset interface and commenting out the auth center tab
in settings. Existing Copilot providers in DB still work via proxy.

src/components/providers/forms/ProviderForm.tsx

@@ -429,10 +429,12 @@ export function ProviderForm({
         preset,
       }));
     }
-    return providerPresets.map<PresetEntry>((preset, index) => ({
-      id: `claude-${index}`,
-      preset,
-    }));
+    return providerPresets
+      .filter((p) => !p.hidden)
+      .map<PresetEntry>((preset, index) => ({
+        id: `claude-${index}`,
+        preset,
+      }));
   }, [appId]);
 
   const {