Replaces browser-cached Basic Auth credentials with proper server-side
session management. Logout now fully invalidates the session. Adds an
HTML login form at /admin/login, SECRET_KEY env var support, and updates
README with key generation instructions and role table.
Swap hand-rolled regex for the email-validator library which handles
RFC 5322 edge cases correctly. check_deliverability=False skips DNS
lookups (not viable on an intranet). Blank email still passes — only
a non-empty, malformed address triggers the error.
Add Flask-Limiter and cap POST submissions to 5 per minute per IP.
GET requests are not limited. Uses in-memory storage (appropriate
for single-instance kiosk deployment).
- Fixed port variable interpolation to use ${PORT:-8000} for a default value.
- Updated volume configuration to use a named volume (guestbook_data) mounted at /data.
- Improved YAML formatting for clarity.