feat: Brainstorm Topics with GSC + Issue #518 fixes + Blog Editor enhancements

Issue #518 - Subscription not updating after checkout:
- Fix stale closure in SubscriptionContext checkout polling (use subscriptionRef)
- Move checkout success polling from InitialRouteHandler into SubscriptionContext
- Remove redundant polling code from InitialRouteHandler
- Fix plan label: 'Free' instead of 'No Plan', proper capitalization
- Add plan refresh button in UserBadge
- Add 'View Costing Details' to UserBadge dropdown
- Rename 'ALwrity Podcast Maker' to 'Podcast Creator' across UI
- Clean subscription=success URL param after verification

Blog Writer WYSIWYG Editor enhancements:
- Per-section preview toggle (view/edit icons)
- Enhanced hover-based toolbar
- Circular SVG progress stats bar with detailed tooltip
- Research tool chips in stats bar footer
- Per-section TTS with useTextToSpeech hook (browser native)
- Full blog preview modal with print/PDF support
- PlayAllTTSButton: sequential playback with progress bar
- OnThisPageNav: floating sidebar with scroll tracking
- Section data attributes for scroll anchoring

GSC Brainstorm Topics feature:
- Backend: gsc_brainstorm_service.py (rule-based + LLM recommendations)
- Backend: POST /gsc/brainstorm endpoint with 3-word minimum validation
- Frontend: gscBrainstorm.ts API client
- Frontend: useGSCBrainstormConnection hook (popup OAuth, no /onboarding redirect)
- Frontend: useGSCBrainstorm hook (connect check + brainstorm call)
- Frontend: GSCBrainstormModal (3-tab results: Opportunities, Gaps, AI Recs)
- Frontend: BrainstormButton (visible at 3+ words, GSC connect overlay)
- Wire BrainstormButton into ManualResearchForm and ResearchAction
- Add blog_writer to gsc_auth router features for ALWRITY_ENABLED_FEATURES

frontend/src/components/BlogWriter/BlogWriterUtils/BlogWriterLandingSection.tsx

@@ -1,4 +1,5 @@
 import React from 'react';
+import { Box, CircularProgress, Typography } from '@mui/material';
 import BlogWriterLanding from '../BlogWriterLanding';
 import ManualResearchForm from '../ManualResearchForm';
 
@@ -8,36 +9,61 @@ interface BlogWriterLandingSectionProps {
   currentPhase: string;
   navigateToPhase: (phase: string) => void;
   onResearchComplete: (research: any) => void;
+  restoreAttempted?: boolean;
 }
 
+const VALID_PHASES = ['research', 'outline', 'content', 'seo', 'publish'];
+
 export const BlogWriterLandingSection: React.FC<BlogWriterLandingSectionProps> = ({
   research,
   copilotKitAvailable,
   currentPhase,
   navigateToPhase,
   onResearchComplete,
+  restoreAttempted = false,
 }) => {
-  // Only show landing/initial content when no research exists
-  // Phase navigation header is always visible, so this is just the initial content
   if (!research) {
-    // Show research form only when user explicitly navigated to research phase (clicked "Start Research")
     if (currentPhase === 'research') {
       return <ManualResearchForm onResearchComplete={onResearchComplete} />;
     }
-    
-    // Default: Always show landing page when no research exists
-    // This ensures landing page is shown on initial load
+
+    if (currentPhase === '' || !VALID_PHASES.includes(currentPhase)) {
+      return (
+        <BlogWriterLanding 
+          onStartWriting={() => {
+            navigateToPhase('research');
+          }}
+        />
+      );
+    }
+
+    if (restoreAttempted) {
+      return (
+        <BlogWriterLanding 
+          onStartWriting={() => {
+            navigateToPhase('research');
+          }}
+        />
+      );
+    }
+
     return (
-      <BlogWriterLanding 
-        onStartWriting={() => {
-          // Navigate to research phase to show the research form
-          navigateToPhase('research');
-        }}
-      />
+      <Box 
+        display="flex" 
+        flexDirection="column" 
+        alignItems="center" 
+        justifyContent="center" 
+        minHeight="300px"
+        gap={2}
+      >
+        <CircularProgress size={32} />
+        <Typography variant="body2" color="text.secondary">
+          Restoring your work...
+        </Typography>
+      </Box>
     );
   }
   
-  // If research exists, don't show landing section (phase content will be shown instead)
   return null;
 };