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

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

Dockerfile

@@ -1,16 +1,42 @@
+# ---------------------------------------------------------------------------
+# APtool Docker image
+# ---------------------------------------------------------------------------
+# Uses the official Python 3.11 slim image as the base. "slim" is a minimal
+# Debian-based image (~45MB) that includes just enough to run Python -- no
+# compilers, man pages, or other extras. This keeps the image small.
 FROM python:3.11-slim
 
+# Set the working directory inside the container. All subsequent COPY, RUN,
+# and CMD instructions will execute relative to /app.
 WORKDIR /app
 
+# Copy requirements.txt first, BEFORE the app code. Docker caches each
+# layer, so if requirements.txt hasn't changed, "pip install" won't re-run
+# even if app.py changes. This speeds up rebuilds significantly.
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
+# Now copy the application code and templates into the image.
+# sites.conf is baked in as a default but gets overridden at runtime
+# by the docker-compose volume mount (see docker-compose.yml).
 COPY app.py .
 COPY templates/ templates/
 COPY sites.conf .
 
+# Create the uploads directory inside the container. At runtime this
+# gets overlaid by a bind mount from the host (./uploads:/app/uploads)
+# so that uploaded photos persist across container restarts.
 RUN mkdir -p uploads
 
+# Document that the app listens on port 5000. This is informational --
+# the actual port mapping is configured in docker-compose.yml.
 EXPOSE 5000
 
+# Run the app with gunicorn (production WSGI server) instead of Flask's
+# built-in dev server. Flags:
+#   -w 2             -- 2 worker processes (handles concurrent requests)
+#   -b 0.0.0.0:5000  -- bind to all interfaces on port 5000
+#   --access-logfile - -- print access logs to stdout (visible in docker logs)
+#   app:app          -- module:variable -- import "app" from app.py, use the
+#                       Flask instance named "app"
 CMD ["gunicorn", "-w", "2", "-b", "0.0.0.0:5000", "--access-logfile", "-", "app:app"]