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/utils/requestManager.js

@@ -0,0 +1,104 @@
+import { serviceAdapters, apiDocs } from '../services/api';
+
+class RequestManager {
+  constructor() {
+    this.pendingRequests = new Map();
+    this.requestTimeouts = new Map();
+  }
+
+  /**
+   * Debounced request function that cancels previous requests of the same type
+   * @param {string} requestType - Type of request (e.g., 'serviceStatus', 'systemData')
+   * @param {Function} requestFunction - The actual request function to execute
+   * @param {number} debounceMs - Debounce delay in milliseconds
+   * @returns {Promise} - Promise that resolves with the request result
+   */
+  async debouncedRequest(requestType, requestFunction, _debounceMs = 1000) {
+    // Cancel any pending request of the same type
+    if (this.pendingRequests.has(requestType)) {
+      const { controller, timeoutId } = this.pendingRequests.get(requestType);
+      controller.abort();
+      clearTimeout(timeoutId);
+    }
+
+    // Create new abort controller for this request
+    const controller = new AbortController();
+    const timeoutId = setTimeout(() => {
+      controller.abort();
+    }, 30000); // 30 second timeout
+
+    // Store the request info
+    this.pendingRequests.set(requestType, { controller, timeoutId });
+
+    try {
+      const result = await requestFunction(controller.signal);
+      this.pendingRequests.delete(requestType);
+      clearTimeout(timeoutId);
+      return result;
+    } catch (error) {
+      this.pendingRequests.delete(requestType);
+      clearTimeout(timeoutId);
+      
+      if (error.name === 'AbortError') {
+        throw new Error('Request was cancelled');
+      }
+      throw error;
+    }
+  }
+
+  /**
+   * Get service status with debouncing
+   */
+  async getServiceStatus(_signal) {
+    const [adaptersResult, docsResult] = await Promise.allSettled([
+      serviceAdapters.health(),
+      apiDocs.health()
+    ]);
+
+    return {
+      adapters: adaptersResult,
+      docs: docsResult
+    };
+  }
+
+  /**
+   * Get system data with debouncing
+   */
+  async getSystemData(_signal) {
+    const [servicesResult, eventsResult] = await Promise.allSettled([
+      serviceAdapters.getServices(),
+      serviceAdapters.getEvents(10)
+    ]);
+
+    return {
+      services: servicesResult,
+      events: eventsResult
+    };
+  }
+
+  /**
+   * Cancel all pending requests
+   */
+  cancelAllRequests() {
+    this.pendingRequests.forEach(({ controller, timeoutId }) => {
+      controller.abort();
+      clearTimeout(timeoutId);
+    });
+    this.pendingRequests.clear();
+  }
+
+  /**
+   * Cancel specific request type
+   */
+  cancelRequest(requestType) {
+    if (this.pendingRequests.has(requestType)) {
+      const { controller, timeoutId } = this.pendingRequests.get(requestType);
+      controller.abort();
+      clearTimeout(timeoutId);
+      this.pendingRequests.delete(requestType);
+    }
+  }
+}
+
+// Export singleton instance
+export const requestManager = new RequestManager();