Add self-hosted usage analytics: pageview tracking + admin stats dashboard

Records pageviews (path, referrer, browser/OS/device, IP, GeoIP country) via
a POST /api/track beacon into a new PageView table, and exposes aggregated
daily/breakdown stats behind a token-gated GET /api/admin/stats endpoint with
brute-force lockout. Frontend gets a /admin dashboard (charts + breakdown
tables) built on recharts, with a switchable per-day pageviews chart.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docker-compose.prod.yaml

@@ -0,0 +1,42 @@
+# Production stack: built images (no bind mounts), nginx serves the built
+# frontend + reverse-proxies Socket.IO, Postgres is internal-only.
+#
+# Usage:
+#   cp .env.example .env   # fill in real secrets
+#   docker compose -f docker-compose.prod.yaml up -d --build
+
+services:
+  db:
+    image: postgres:18-alpine
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+      POSTGRES_DB: ${POSTGRES_DB}
+    volumes:
+      - pgdata:/var/lib/postgresql
+    restart: always
+
+  backend:
+    build: .
+    environment:
+      DATABASE_URL: postgresql+asyncpg://${POSTGRES_USER}:${POSTGRES_PASSWORD}@db:5432/${POSTGRES_DB}
+      CORS_ALLOWED_ORIGINS: ${CORS_ALLOWED_ORIGINS}
+      ADMIN_TOKEN: ${ADMIN_TOKEN}
+      ENCRYPTION_KEY: ${ENCRYPTION_KEY}
+      GEOIP_DB_PATH: /app/geoip/GeoLite2-Country.mmdb
+    volumes:
+      - ./geoip:/app/geoip:ro
+    restart: always
+    depends_on:
+      - db
+
+  frontend:
+    build: ./frontend
+    environment:
+      BACKEND_UPSTREAM: backend:5000
+    restart: always
+    depends_on:
+      - backend
+
+volumes:
+  pgdata: