feat: add analytics dashboard with traffic monitoring

- Parse Caddy access logs every 30s into traffic_events SQLite table
- GeoIP country lookup via maxmind (GeoLite2-Country.mmdb)
- 90-day retention with automatic purge
- Analytics page with interval (24h/7d/30d) and per-host filtering:
  - Stats cards: total requests, unique IPs, blocked count, block rate
  - Requests-over-time area chart (ApexCharts)
  - SVG world choropleth map (d3-geo + topojson-client, React 19 compatible)
  - Top countries table with flag emojis
  - HTTP protocol donut chart
  - Top user agents horizontal bar chart
  - Recent blocked requests table with pagination
- Traffic (24h) summary card on Overview page linking to analytics
- 7 authenticated API routes under /api/analytics/
- Share caddy-logs volume with web container (read-only)
- group_add caddy GID to web container for log file read access

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

docker-compose.yml

@@ -52,9 +52,12 @@ services:
       OAUTH_TOKEN_URL: ${OAUTH_TOKEN_URL:-}
       OAUTH_USERINFO_URL: ${OAUTH_USERINFO_URL:-}
       OAUTH_ALLOW_AUTO_LINKING: ${OAUTH_ALLOW_AUTO_LINKING:-false}
+    group_add:
+      - "${CADDY_GID:-10000}"  # caddy's GID — lets the web user read /logs/access.log
     volumes:
       - caddy-manager-data:/app/data
       - geoip-data:/usr/share/GeoIP:ro,z
+      - caddy-logs:/logs:ro
     depends_on:
       caddy:
         condition: service_healthy