Add detailed inline comments to app.py, Dockerfile, and docker-compose.yml

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -1,11 +1,37 @@
+# ---------------------------------------------------------------------------
+# APtool Docker Compose configuration
+# ---------------------------------------------------------------------------
+# Run with: docker compose up -d --build
+# Logs:     docker compose logs -f aptool
+# Rebuild:  docker compose up -d --build  (after code changes)
+# Stop:     docker compose down
+# ---------------------------------------------------------------------------
 services:
   aptool:
+    # Build the image from the Dockerfile in this directory (.)
     build: .
+
+    # Map host port 5000 -> container port 5000.
+    # Access the app at http://<host-ip>:5000
     ports:
       - "5000:5000"
+
     volumes:
+      # Bind-mount the uploads directory so photos persist outside the
+      # container. Without this, uploaded files would be lost on restart.
       - ./uploads:/app/uploads
+
+      # Bind-mount sites.conf so you can edit it on the host without
+      # rebuilding the image. The app re-reads this file on every login
+      # attempt, so changes take effect immediately.
       - ./sites.conf:/app/sites.conf
+
+    # Load environment variables from .env file. This file contains
+    # sensitive Nextcloud credentials (NC_URL, NC_USER, NC_PASS) and
+    # the Flask SECRET_KEY. It is excluded from git via .gitignore.
     env_file:
       - .env
+
+    # Restart the container automatically unless explicitly stopped
+    # with "docker compose down" or "docker stop". Survives host reboots.
     restart: unless-stopped