feat: Enhance frontend loading experience and service status handling

### Summary of Changes
- Removed proxy configuration in `rsbuild.config.js` as the API Gateway is not running.
- Added smooth transitions and gentle loading overlays in CSS for improved user experience during data loading.
- Updated `Dashboard` component to conditionally display loading spinner and gentle loading overlay based on data fetching state.
- Enhanced `useOfflineAwareServiceStatus` and `useOfflineAwareSystemData` hooks to manage loading states and service status more effectively.
- Increased refresh intervals for service status and system data to reduce API call frequency.

### Expected Results
- Improved user experience with smoother loading transitions and better feedback during data refreshes.
- Enhanced handling of service status checks, providing clearer information when services are unavailable.
- Streamlined code for managing loading states, making it easier to maintain and extend in the future.

frontend/src/hooks/useGentleLoading.js

@@ -0,0 +1,42 @@
+import { useState, useCallback } from 'react';
+
+export const useGentleLoading = (initialLoading = false) => {
+  const [loading, setLoading] = useState(initialLoading);
+  const [refreshing, setRefreshing] = useState(false);
+
+  const startLoading = useCallback(() => {
+    setLoading(true);
+  }, []);
+
+  const stopLoading = useCallback(() => {
+    setLoading(false);
+  }, []);
+
+  const startRefreshing = useCallback(() => {
+    setRefreshing(true);
+  }, []);
+
+  const stopRefreshing = useCallback(() => {
+    setRefreshing(false);
+  }, []);
+
+  const withGentleLoading = useCallback(async (asyncFunction) => {
+    try {
+      setRefreshing(true);
+      const result = await asyncFunction();
+      return result;
+    } finally {
+      setRefreshing(false);
+    }
+  }, []);
+
+  return {
+    loading,
+    refreshing,
+    startLoading,
+    stopLoading,
+    startRefreshing,
+    stopRefreshing,
+    withGentleLoading
+  };
+};