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/styles/global.css

@@ -418,4 +418,25 @@ html.blog-writer-page {
 
 .blog-writer-container .MuiTextField-root .MuiOutlinedInput-root fieldset {
   border-color: rgba(26, 26, 26, 0.23) !important;
+}
+
+/* Hide CopilotKit Web Inspector button and announcement globally */
+cpk-web-inspector {
+  display: none !important;
+  visibility: hidden !important;
+  pointer-events: none !important;
+  position: absolute !important;
+  left: -9999px !important;
+  width: 0 !important;
+  height: 0 !important;
+  overflow: hidden !important;
+}
+
+[class*="copilotkit"] [class*="announcement"],
+[class*="copilotkit"] [class*="announce"],
+.announcement-preview,
+[data-announcement],
+.cpk-announcement {
+  display: none !important;
+  visibility: hidden !important;
 }