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/components/BlogWriter/EnhancedOutlineEditor.tsx

@@ -910,16 +910,25 @@ const EnhancedOutlineEditor: React.FC<Props> = ({
           defaultPrompt={getSectionHeading(imageModalState.sectionId)}
           context={getSectionContext(imageModalState.sectionId)}
           onImageGenerated={(imageBase64, sectionId) => { 
+            console.time('[SectionImages] onImageGenerated');
             if (sectionId && setSectionImages) { 
               setSectionImages((prev: Record<string, string>) => ({ ...prev, [sectionId]: imageBase64 })); 
               try {
                 const existing = JSON.parse(localStorage.getItem('blog_section_images') || '{}');
                 existing[sectionId] = imageBase64;
-                localStorage.setItem('blog_section_images', JSON.stringify(existing));
+                const serialized = JSON.stringify(existing);
+                if (serialized.length > 4_000_000) {
+                  console.warn(`[SectionImages] Approaching localStorage quota: ${(serialized.length / 1024 / 1024).toFixed(1)}MB`);
+                }
+                localStorage.setItem('blog_section_images', serialized);
+                console.timeLog('[SectionImages] onImageGenerated', `saved sectionId=${sectionId} base64_len=${imageBase64.length}`);
               } catch (e) {
                 console.warn('[SectionImages] Failed to persist to localStorage:', e);
               }
-            } 
+            } else {
+              console.warn('[SectionImages] Skipped: sectionId=', sectionId, 'setSectionImages=', !!setSectionImages);
+            }
+            console.timeEnd('[SectionImages] onImageGenerated');
           }}
         />
       )}