docs: update documentation with Activity Log System implementation

Updated all major documentation files to reflect the completed Activity
Log System (Phase 3.5) implementation.

Changes:
- README.md: Added Admin & Monitoring section, updated database schema
  to 12 tables, added Activity Log System to completed phases, updated
  project structure to show admin pages and services
- SESSION_CONTEXT.md: Updated recent work, added activity log system to
  core features, updated database schema, added comprehensive Phase 3.5
  overview with all implementation details
- COMPLETED.md: Added full Activity Log System entry with all 8 phases,
  implementation details, git commits, and access information

Updated dates to 2025-12-02.

README.md

@@ -71,10 +71,18 @@ Web application (PWA) enabling dance event participants to:
 - Location (country + city with 195 countries)
 - Profile statistics (matches, average rating, reviews)
 
+### Admin & Monitoring
+- Activity Log System with real-time streaming dashboard
+- Comprehensive audit trail (auth, events, matches, chat, admin actions)
+- Filter logs by date range, action type, category, username, success/failure
+- Real-time Socket.IO streaming (like `tail -f`)
+- Admin-only access with requireAdmin middleware
+- Statistics dashboard (total logs, failures, 24h activity)
+
 ### PWA & Infrastructure
 - Progressive Web App (offline support, iOS compatible)
 - Docker Compose orchestration (nginx, frontend, backend, PostgreSQL)
-- PostgreSQL 15 with Prisma ORM (11 tables)
+- PostgreSQL 15 with Prisma ORM (12 tables)
 - Admin CLI with REPL for operations
 
 ---
@@ -184,6 +192,7 @@ spotlightcam/
 │   ├── src/
 │   │   ├── components/        # React components
 │   │   ├── pages/             # Application pages
+│   │   │   └── admin/         # Admin pages (ActivityLogsPage)
 │   │   ├── hooks/             # Custom hooks (useWebRTC)
 │   │   ├── contexts/          # AuthContext
 │   │   ├── services/          # API client, Socket.IO client
@@ -194,11 +203,12 @@ spotlightcam/
 │   ├── src/
 │   │   ├── controllers/       # Auth, users, events, WSDC
 │   │   ├── routes/            # API routes (events, matches, admin)
-│   │   ├── services/          # Matching algorithm
-│   │   ├── socket/            # Socket.IO handlers (chat, WebRTC signaling)
+│   │   ├── services/          # Matching algorithm, activity logging
+│   │   ├── middleware/        # Auth, admin access control
+│   │   ├── socket/            # Socket.IO handlers (chat, WebRTC signaling, admin logs)
 │   │   └── __tests__/         # Jest tests (342 tests)
 │   ├── prisma/
-│   │   ├── schema.prisma      # Database schema (11 tables)
+│   │   ├── schema.prisma      # Database schema (12 tables)
 │   │   └── migrations/        # Database migrations
 │   ├── Dockerfile             # Development container
 │   └── Dockerfile.prod        # Production build
@@ -217,10 +227,10 @@ spotlightcam/
 
 ## 🗄️ Database Schema
 
-11 tables with relations (Prisma ORM):
+12 tables with relations (Prisma ORM):
 
 **Core Tables:**
-- `users` - Authentication, profile, social links, location, account tiers
+- `users` - Authentication, profile, social links, location, account tiers, isAdmin flag
 - `events` - Dance events with unique slugs
 - `event_participants` - User-event relationship, competitor numbers
 - `matches` - User pairings with CUID slugs
@@ -232,6 +242,9 @@ spotlightcam/
 - `recording_suggestions` - Auto-matching results with collision detection, originRunId
 - `matching_runs` - Audit trail (manual/scheduler, status, stats)
 
+**Admin & Monitoring:**
+- `activity_logs` - Comprehensive audit trail with 18 action types, indexed for performance
+
 **Other:**
 - `event_checkin_tokens` - QR code check-in
 
@@ -327,6 +340,7 @@ docker compose exec backend npm run cli -- matches:list --limit 20 --status acce
 **Phase 2:** Matches & ratings API, message history
 **Phase 2.5:** WebRTC P2P file transfer with fallback UX
 **Phase 3:** MVP finalization (landing page, dashboard, security hardening, PWA, auto-matching)
+**Phase 3.5:** Activity Log System (admin monitoring, real-time streaming dashboard, 18 action types)
 
 ### ⏳ Future Extensions (Phase 4)
 - User badges & trust system
@@ -362,4 +376,4 @@ TBD
 ---
 
 **Status:** MVP Complete ✅ | 342/342 tests passing (100%) | Production Ready
-**Last Updated:** 2025-11-30
+**Last Updated:** 2025-12-02