Add calendar app — shared events calendar with departments, staff tagging, bank holidays and two-way phone sync

Fastify/Postgres backend + React frontend matching the stack's app conventions, plus
a hand-rolled RFC 4791 CalDAV server (caldav-adapter turned out Koa-only in practice)
so calendars subscribe as genuine two-way sync in Apple/Google/Outlook. v1 scope:
multiple colour-coded calendars, department/staff event tagging via live Workforce
lookups, month/week/day/list views, dashboard, file attachments, activity log, and
an auto-synced UK bank holidays calendar. Verified end-to-end locally against real
Postgres: REST CRUD, CalDAV discovery/PROPFIND/REPORT/PUT/sync-collection, all-day
date handling, system-calendar write protection, and activity logging across both
the web and CalDAV write paths.

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

docker-compose.yml

@@ -0,0 +1,41 @@
+services:
+  backend:
+    build: ./backend
+    security_opt:
+      - apparmor=unconfined
+    environment:
+      - DATABASE_URL=${DATABASE_URL}
+      - CENTRAL_AUTH_SECRET=${CENTRAL_AUTH_SECRET}
+      - SETTINGS_URL=${SETTINGS_URL}
+      - SETTINGS_SECRET=${SETTINGS_SECRET}
+      - APP_SLUG=calendar
+      - OFFICE_IP_CHECK=${OFFICE_IP_CHECK:-disabled}
+    volumes:
+      - uploads_data:/app/uploads
+    healthcheck:
+      test: ["CMD-SHELL", "wget -qO- http://127.0.0.1:3001/health || exit 1"]
+      interval: 10s
+      retries: 5
+      start_period: 20s
+    restart: unless-stopped
+
+  frontend:
+    build:
+      context: ./frontend
+      args:
+        VITE_HOTEL_NAME: ${VITE_HOTEL_NAME}
+    security_opt:
+      - apparmor=unconfined
+    ports:
+      - "${FRONTEND_PORT:-3080}:80"
+    depends_on:
+      backend:
+        condition: service_healthy
+    restart: unless-stopped
+
+networks:
+  default:
+    driver: bridge
+
+volumes:
+  uploads_data: