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

backend/routers/gsc_auth.py

@@ -8,6 +8,7 @@ from loguru import logger
 import os
 
 from services.gsc_service import GSCService
+from services.gsc_brainstorm_service import GSCBrainstormService
 from middleware.auth_middleware import get_current_user
 
 # Initialize router
@@ -15,6 +16,7 @@ router = APIRouter(prefix="/gsc", tags=["Google Search Console"])
 
 # Initialize GSC service
 gsc_service = GSCService()
+brainstorm_service = GSCBrainstormService(gsc_service)
 
 # Pydantic models
 class GSCAnalyticsRequest(BaseModel):
@@ -22,6 +24,10 @@ class GSCAnalyticsRequest(BaseModel):
     start_date: Optional[str] = None
     end_date: Optional[str] = None
 
+class GSCBrainstormRequest(BaseModel):
+    keywords: str
+    site_url: Optional[str] = None
+
 class GSCStatusResponse(BaseModel):
     connected: bool
     sites: Optional[List[Dict[str, Any]]] = None
@@ -199,6 +205,49 @@ async def get_gsc_analytics(
         logger.error(f"Error getting GSC analytics: {e}")
         raise HTTPException(status_code=500, detail=f"Error getting analytics: {str(e)}")
 
+@router.post("/brainstorm")
+async def brainstorm_topics(
+    request: GSCBrainstormRequest,
+    user: dict = Depends(get_current_user),
+):
+    """Brainstorm blog topic suggestions based on the user's GSC data.
+
+    The user must have GSC connected. If no site_url is provided,
+    the first verified site is used automatically.
+    """
+    try:
+        user_id = user.get('id')
+        if not user_id:
+            raise HTTPException(status_code=400, detail="User ID not found")
+
+        tokens = request.keywords.strip().split()
+        if len(tokens) < 3:
+            raise HTTPException(
+                status_code=400,
+                detail="Please provide at least 3 words for brainstorming topic suggestions.",
+            )
+
+        logger.info(f"GSC brainstorm for user: {user_id}, keywords: {request.keywords!r}")
+
+        result = brainstorm_service.brainstorm_topics(
+            user_id=user_id,
+            keywords=request.keywords,
+            site_url=request.site_url,
+        )
+
+        if "error" in result and not result.get("content_opportunities"):
+            status = 400 if "No GSC sites" in result["error"] else 500
+            raise HTTPException(status_code=status, detail=result["error"])
+
+        logger.info(f"GSC brainstorm completed for user: {user_id}")
+        return result
+
+    except HTTPException:
+        raise
+    except Exception as e:
+        logger.error(f"Error in GSC brainstorm: {e}")
+        raise HTTPException(status_code=500, detail=f"Error brainstorming topics: {str(e)}")
+
 @router.get("/sitemaps/{site_url:path}")
 async def get_gsc_sitemaps(
     site_url: str,