fix: add explicit GET method to API requests and make refresh interval reactive

- Add explicit method: 'GET' to ApiProxy.request() calls in polaris.ts and PolarisSettings.tsx
  for compatibility with Headlamp SDK
- Make refresh interval reactive by polling localStorage every second in PolarisDataContext
  so settings changes take effect immediately without page reload

Fixes connection test button and data refresh issues.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

src/components/PolarisSettings.tsx

@@ -58,7 +58,9 @@ export default function PolarisSettings(props: PluginSettingsProps) {
         }
         result = await response.json();
       } else {
-        result = await ApiProxy.request(apiPath);
+        result = await ApiProxy.request(apiPath, {
+          method: 'GET',
+        });
       }
 
       setTestResult({