feat(phase-6): WS3+WS4+WS6 — Analytics, API Tiers, AGNTCY Compliance

WS3 — Advanced Analytics Dashboard:
- DB migration: analytics_events table (tenant_id, date, metric_type, count)
- AnalyticsService: recordEvent (fire-and-forget), getTokenTrend, getAgentActivity, getAgentUsageSummary
- Analytics hooks in OAuth2Service (token_issued) and AgentService (agent_registered/deactivated)
- AnalyticsController + routes/analytics.ts (gated by ANALYTICS_ENABLED flag)
- Portal: TokenTrendChart (recharts LineChart), AgentHeatmap (recharts heatmap), /analytics page

WS4 — API Gateway Tiers:
- DB migration: tenant_tiers table; src/config/tiers.ts (free/pro/enterprise limits)
- TierService: getStatus, initiateUpgrade (Stripe), applyUpgrade; TierLimitError in errors.ts
- tierEnforcement middleware (Redis-backed daily call/token counters; TIER_ENFORCEMENT flag)
- Agent count enforcement in AgentService.create()
- Stripe webhook updated to call TierService.applyUpgrade() on checkout.session.completed
- TierController + routes/tiers.ts; Portal: /settings/tier page with upgrade flow

WS6 — AGNTCY Compliance Certification:
- ComplianceService: generateReport() (Redis-cached 5 min), exportAgentCards()
- Compliance sections: agent-identity (DID + credential expiry checks), audit-trail (Merkle chain)
- ComplianceController updated with getComplianceReport, exportAgentCards handlers
- routes/compliance.ts: new AGNTCY routes (gated by COMPLIANCE_ENABLED flag); SOC2 routes unaffected

QA:
- 28 new unit tests: AnalyticsService (8), TierService (9), ComplianceService (11) — all pass
- 673 total unit tests passing; 0 TypeScript errors across API and portal
- AGNTCY conformance test suite at tests/agntcy-conformance/ (4 protocol tests)
- Portal builds cleanly: 9 routes including /analytics and /settings/tier
- Feature flags verified: ANALYTICS_ENABLED, TIER_ENFORCEMENT, COMPLIANCE_ENABLED

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

portal/components/Nav.tsx

@@ -15,6 +15,7 @@ const links: NavLink[] = [
   { href: '/get-started', label: 'Get Started' },
   { href: '/sdks', label: 'SDKs' },
   { href: '/pricing', label: 'Pricing' },
+  { href: '/analytics', label: 'Analytics' },
 ];
 
 export function Nav(): React.ReactElement {