Add graceful error handling for subscription mode wallet dependency

- Detect wallet service unavailable errors and show clear user message
- Explain Bitcoin payment requirement and wallet service dependency
- Automatically revert to previous mode when subscription mode fails
- Prevent UI from getting stuck in inconsistent state
- Increase error message duration for better readability

Author: Maphikza

src/components/allowed-users/layouts/AllowedUsersLayout.tsx

@@ -77,6 +77,16 @@ export const AllowedUsersLayout: React.FC = () => {
     try {
       await updateSettings(localSettings);
       setHasChanges(false);
+    } catch (error) {
+      // If save fails due to wallet service, reset to previous mode
+      if (localSettings.mode === 'subscription' && 
+          error instanceof Error && 
+          error.message.includes('wallet service')) {
+        console.log('Reverting to previous mode due to wallet service error');
+        setLocalSettings(settings);
+        setCurrentMode(settings.mode);
+        setHasChanges(false);
+      }
     } finally {
       setSaving(false);
     }

src/hooks/useAllowedUsers.ts

@@ -50,8 +50,19 @@ export const useAllowedUsersSettings = () => {
       message.success('Settings updated successfully');
     } catch (err) {
       const errorMessage = err instanceof Error ? err.message : 'Failed to update settings';
-      setError(errorMessage);
-      message.error(errorMessage);
+      
+      // Handle specific wallet service error for subscription mode
+      if (errorMessage.includes('wallet service is not available') || 
+          errorMessage.includes('cannot switch to subscription mode')) {
+        setError('Subscription mode requires active wallet service');
+        message.error({
+          content: 'Subscription mode requires Bitcoin payments, but the relay wallet service is not running. Please start the wallet service to generate Bitcoin addresses for user payments before enabling subscription mode.',
+          duration: 8
+        });
+      } else {
+        setError(errorMessage);
+        message.error(errorMessage);
+      }
       throw err;
     } finally {
       setLoading(false);