Update compose + CI for CasaOS deploy; build both images in CI

docker-compose.yml:
- Remove env_file — all vars inline with \${VAR:-default} substitution
- NTFY_TOPIC soft-defaults to empty (no hard :? error)
- Pull pre-built images from ghcr.io (no local build step)
- Add resource limits: app 512MB/1CPU, notifier 128MB/0.25CPU
- Add x-casaos metadata for CasaOS app store / dashboard
- Remove dev service (run separately as needed)

.github/workflows/docker.yml:
- Build and push both app (ghcr.io/nmemmert/letter) and notifier
  (ghcr.io/nmemmert/letter-notifier) images in one job
- Separate GHA cache scopes per image for efficient layer reuse
- Separate metadata steps for independent tag sets

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

docker-compose.yml

@@ -1,66 +1,49 @@
 services:
-
-  # ── Web app (nginx, port 8080) ──────────────────────────────────────────────
   app:
-    build: .
-    image: ghcr.io/nmemmert/letter:main
+    image: "ghcr.io/nmemmert/letter:main"
+    deploy:
+      resources:
+        reservations:
+          memory: 128MB
+          cpus: "0.00"
+        limits:
+          memory: 512MB
+          cpus: "1.00"
+    restart: no
+    network_mode: bridge
     ports:
       - "${APP_PORT:-8080}:80"
-    restart: unless-stopped
+    volumes: []
 
-  # ── Monthly ntfy reminder ───────────────────────────────────────────────────
   notifier:
-    build: ./notifier
-    restart: unless-stopped
-    env_file:
-      - path: .env
-        required: false        # container still starts without a .env file
+    image: "ghcr.io/nmemmert/letter-notifier:main"
+    deploy:
+      resources:
+        reservations:
+          memory: 64MB
+          cpus: "0.00"
+        limits:
+          memory: 128MB
+          cpus: "0.25"
+    restart: no
+    network_mode: bridge
+    volumes: []
     environment:
-      # ── ntfy connection ───────────────────────────────────────────────────
-      # Required: your ntfy topic — keep it unguessable, e.g. "nate-letter-k7x2"
-      # Subscribe at https://ntfy.sh/<NTFY_TOPIC> or in the ntfy mobile app
-      NTFY_TOPIC: ${NTFY_TOPIC:?NTFY_TOPIC is required — set it in .env}
-
-      # ntfy server (default: ntfy.sh; set to your self-hosted URL if applicable)
-      NTFY_URL: ${NTFY_URL:-https://ntfy.sh}
-
-      # Bearer token for access-controlled / private topics (leave blank for public)
-      NTFY_TOKEN: ${NTFY_TOKEN:-}
-
-      # Notification priority: min | low | default | high | urgent
-      NTFY_PRIORITY: ${NTFY_PRIORITY:-default}
-
-      # ── Schedule ──────────────────────────────────────────────────────────
-      # Cron expression — default fires at 9 AM on the 1st of every month
-      # Format: minute hour day-of-month month day-of-week
-      CRON_SCHEDULE: ${CRON_SCHEDULE:-0 9 1 * *}
-
-      # IANA timezone for the cron schedule
-      TZ: ${TZ:-America/Chicago}
-
-      # ── App ───────────────────────────────────────────────────────────────
-      # URL the notification deep-links back to (shown as "Open" in ntfy)
-      APP_URL: ${APP_URL:-http://localhost:8080}
-
-      # Set to "true" to fire a test notification immediately on container start
-      NTFY_TEST_ON_START: ${NTFY_TEST_ON_START:-false}
-
+      - NTFY_TOPIC=${NTFY_TOPIC:-}
+      - NTFY_URL=${NTFY_URL:-https://ntfy.sh}
+      - NTFY_TOKEN=${NTFY_TOKEN:-}
+      - NTFY_PRIORITY=${NTFY_PRIORITY:-default}
+      - CRON_SCHEDULE=${CRON_SCHEDULE:-0 9 1 * *}
+      - TZ=${TZ:-America/Chicago}
+      - APP_URL=${APP_URL:-http://172.16.16.106:8080}
+      - NTFY_TEST_ON_START=${NTFY_TEST_ON_START:-false}
     depends_on:
       - app
 
-  # ── Local dev (Vite HMR, port 5173) — run with: docker compose --profile dev up dev
-  dev:
-    image: node:20-alpine
-    working_dir: /app
-    volumes:
-      - .:/app
-      - node_modules:/app/node_modules
-    ports:
-      - "${DEV_PORT:-5173}:5173"
-    environment:
-      NODE_ENV: development
-    command: sh -c "npm install && npm run dev -- --host 0.0.0.0"
-    profiles: [dev]
-
-volumes:
-  node_modules:
+x-casaos:
+  title:
+    custom: "Annual Letter"
+  main: app
+  scheme: http
+  hostname: "172.16.16.106"
+  index: /