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/SEOAnalysisModal.tsx

@@ -166,6 +166,7 @@ export const SEOAnalysisModal: React.FC<SEOAnalysisModalProps> = ({
   const [contentHash, setContentHash] = useState<string>('');
   const [isApplying, setIsApplying] = useState(false);
   const [applyError, setApplyError] = useState<string | null>(null);
+  const [fromCache, setFromCache] = useState(false);
 
   // Debug logging only in development and when modal state changes meaningfully
   useEffect(() => {
@@ -213,6 +214,7 @@ export const SEOAnalysisModal: React.FC<SEOAnalysisModalProps> = ({
             // Validate cached data has required fields
             if (parsed && typeof parsed.overall_score === 'number' && parsed.category_scores) {
               console.log('✅ Using cached SEO analysis', { cacheKey, overall_score: parsed.overall_score });
+              setFromCache(true);
               setAnalysisResult(parsed);
               setIsAnalyzing(false);
               setProgress(100);
@@ -322,6 +324,7 @@ export const SEOAnalysisModal: React.FC<SEOAnalysisModalProps> = ({
         generated_at: new Date().toISOString()
       };
       
+      setFromCache(false);
       setAnalysisResult(convertedResult);
 
       // Save to cache - use the same cacheKey that was used for checking
@@ -482,6 +485,14 @@ export const SEOAnalysisModal: React.FC<SEOAnalysisModalProps> = ({
               <Typography variant="h5" component="h2" sx={{ fontWeight: 600 }}>
                 SEO Analysis Results
               </Typography>
+              {fromCache && analysisResult?.generated_at && (
+                <Chip
+                  label={`Cached: ${new Date(analysisResult.generated_at).toLocaleString()}`}
+                  size="small"
+                  variant="outlined"
+                  sx={{ fontSize: '0.7rem', height: 22, color: '#64748b', borderColor: '#cbd5e1' }}
+                />
+              )}
             </Box>
             <Box sx={{ display: 'flex', alignItems: 'center', gap: 1 }}>
               <Button
@@ -493,7 +504,7 @@ export const SEOAnalysisModal: React.FC<SEOAnalysisModalProps> = ({
                   runSEOAnalysis(true);
                 }}
               >
-                Refresh
+                {fromCache ? 'Re-Run Analysis' : 'Run Analysis'}
               </Button>
               <IconButton onClick={onClose} sx={{ color: 'text.secondary' }}>
                 <Close />