feat: ContentGuardianAgent, onboarding UX, Team Activity action wiring, docs, agent help modal

ContentGuardianAgent consolidation:
- Merge 3 duplicate classes into single source in specialized/content_guardian.py
- Watchdog audit_committee() with heuristic scoring, coverage gaps, overlaps, alerts
- Remove misleading rejection_rate() helper; use acceptance_rate directly
- Integrate audit + alerts + trend signals into today_workflow_service.py

Team Activity page:
- QualityAuditPanel: health ring, per-agent critiques, coverage gaps, overlaps
- TrendSignalsPanel: opportunity cards with urgency/impact/coverage bars
- AlertBanner: persistent dismiss via POST /alerts/{id}/mark-read
- AgentHelpModal: dialog showing all 8 agents with descriptions, tools, schedule
- QualityAuditPanel action buttons: Fill gap -> /content-planning, Resolve overlap, View CTA on alerts/issues
- TrendSignalsPanel action buttons: Create content from this trend -> /blog-writer with trend context state

Onboarding system:
- Step 4 validation: no auto-pass via basic_ready; requires persona data or explicit progression
- Step 5 validation: logs warning on auto-pass without integration data
- OnboardingCompletionService: single DB session, transactional task creation, upsert pattern
- Business-without-website: nullable website_url on SIFIndexingTask and MarketTrendsTask
- DeepCompetitorAnalysisExecutor: 5-min timeout, 10-competitor cap, asyncio.wait_for
- Persona generation: async with 30s timeout, falls back to scheduler
- OnboardingProgressService.reset_onboarding(): resets session + pauses all DB tasks
- OnboardingControlService.reset_onboarding(): also cancels APScheduler jobs
- FinalStep TaskSchedulingPanel: shows scheduled/failed tasks after completion, 8s auto-redirect
- onboarding_completed agent activity event logged to feed

Documentation:
- docs-site/features/onboarding/: overview, steps, scheduler-tasks, technical-reference (4 pages)
- docs-site/mkdocs.yml: added Onboarding System nav section
- docs-site/features/sif-agents/: overview, agent-directory, committee-system, content-guardian (4 pages)
- docs-site/features/team-activity/: overview, quality-audit, trend-signals, alert-system (4 pages)
- docs-site/features/todays-workflow/: updated overview, technical-architecture, workflow-guide, api-reference

frontend/src/hooks/useBlogWriterState.ts

@@ -95,11 +95,14 @@ const restoreInitialState = () => {
     seoAnalysis = readLS<BlogSEOAnalyzeResponse | null>('blog_seo_analysis', null);
     seoMetadata = readLS<BlogSEOMetadataResponse | null>('blog_seo_metadata', null);
 
-    // Restore section images
+    // Restore section images (log only once per session, not on every hook mount)
     const savedSectionImages = readLS<Record<string, string> | null>('blog_section_images', null);
     if (savedSectionImages && Object.keys(savedSectionImages).length > 0) {
       sectionImages = savedSectionImages;
-      console.log(`[SectionImages] Restored ${Object.keys(sectionImages).length} images from localStorage`);
+      if (!(window as any).__sectionImagesLogged) {
+        console.log(`[SectionImages] Restored ${Object.keys(sectionImages).length} images from localStorage`);
+        (window as any).__sectionImagesLogged = true;
+      }
     }
   } catch (error) {
     console.error('Error during initial state restoration:', error);
@@ -137,6 +140,7 @@ export const useBlogWriterState = () => {
   const [seoAnalysis, setSeoAnalysis] = useState<BlogSEOAnalyzeResponse | null>(initialState.seoAnalysis);
   const [genMode, setGenMode] = useState<'draft' | 'polished'>('polished');
   const [seoMetadata, setSeoMetadata] = useState<BlogSEOMetadataResponse | null>(initialState.seoMetadata);
+  const [introduction, setIntroduction] = useState<string>(localStorage.getItem('blog_introduction') || '');
   const [continuityRefresh, setContinuityRefresh] = useState<number>(0);
   const [outlineTaskId, setOutlineTaskId] = useState<string | null>(null);
   const [flowAnalysisCompleted, setFlowAnalysisCompleted] = useState<boolean>(false);
@@ -246,15 +250,32 @@ export const useBlogWriterState = () => {
   useEffect(() => {
     try {
       if (Object.keys(sectionImages).length > 0) {
-        localStorage.setItem('blog_section_images', JSON.stringify(sectionImages));
+        const serialized = JSON.stringify(sectionImages);
+        // Warn if approaching localStorage quota (~5MB)
+        if (serialized.length > 4_000_000) {
+          console.warn(`[SectionImages] Approaching localStorage quota: ${(serialized.length / 1024 / 1024).toFixed(1)}MB`);
+        }
+        localStorage.setItem('blog_section_images', serialized);
       } else {
-        localStorage.removeItem('blog_section_images');
+        // Only remove if we have previously saved images (avoid clearing on transient empty state)
+        if (localStorage.getItem('blog_section_images')) {
+          localStorage.removeItem('blog_section_images');
+        }
       }
     } catch (e) {
       console.warn('[SectionImages] Failed to persist to localStorage via effect:', e);
     }
   }, [sectionImages]);
 
+  // Persist introduction to localStorage whenever it changes
+  useEffect(() => {
+    try {
+      if (introduction) {
+        localStorage.setItem('blog_introduction', introduction);
+      }
+    } catch {}
+  }, [introduction]);
+
   // Persist sections to blogWriterCache whenever they change
   useEffect(() => {
     const outlineIds = outline.map(s => String(s.id));
@@ -410,6 +431,7 @@ export const useBlogWriterState = () => {
     titleOptions,
     selectedTitle,
     sections,
+    introduction,
     seoAnalysis,
     genMode,
     seoMetadata,
@@ -433,6 +455,7 @@ export const useBlogWriterState = () => {
     setTitleOptions,
     setSelectedTitle,
     setSections,
+    setIntroduction,
     setSeoAnalysis,
     setGenMode,
     setSeoMetadata,