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/services/linkApi.ts

@@ -0,0 +1,69 @@
+import { aiApiClient } from '../api/client';
+
+export interface LinkSearchRequest {
+  query: string;
+  link_type: 'internal' | 'external';
+  site_url?: string;
+  num_results?: number;
+}
+
+export interface LinkSearchResult {
+  title: string;
+  url: string;
+  text: string;
+  publishedDate: string;
+  author: string;
+  score: number;
+}
+
+export interface LinkSearchResponse {
+  results: LinkSearchResult[];
+  warnings: string[];
+}
+
+export interface RewordRequest {
+  section_text: string;
+  selected_text?: string;
+  section_heading?: string;
+  links: Array<{ url: string; title: string }>;
+}
+
+export interface RewordResponse {
+  reworded_text: string;
+  warnings: string[];
+}
+
+class LinkApiService {
+  private baseUrl: string;
+
+  constructor() {
+    const url = process.env.REACT_APP_API_URL;
+    if (process.env.NODE_ENV === 'production' && !url) {
+      throw new Error('REACT_APP_API_URL environment variable is required for production');
+    }
+    this.baseUrl = url || 'http://localhost:8000';
+  }
+
+  async searchLinks(params: LinkSearchRequest): Promise<LinkSearchResponse> {
+    const { data } = await aiApiClient.post('/api/links/search', {
+      query: params.query,
+      link_type: params.link_type,
+      site_url: params.site_url || '',
+      num_results: params.num_results || 5,
+    });
+    return data;
+  }
+
+  async rewordWithLinks(params: RewordRequest): Promise<RewordResponse> {
+    const { data } = await aiApiClient.post('/api/links/reword', {
+      section_text: params.section_text,
+      selected_text: params.selected_text,
+      section_heading: params.section_heading,
+      links: params.links,
+    });
+    return data;
+  }
+}
+
+export const linkApi = new LinkApiService();
+export default linkApi;