Add in-app help page with user manual (Romanian)

Adds a /help page served from the dashboard navigation, containing the full
Romanian user manual for operators: dashboard, playlist management, adding
media, removing files from playlists, player management, and the advanced
edited-media view.

Implementation notes
- Manual is pre-rendered to HTML with pandoc and shipped as a static asset
  (app/static/help/_manual_body.html) rather than parsed at runtime. This
  keeps the container free of a Markdown dependency and makes the page render
  identically regardless of what is installed.
- /help is login-protected; the sidebar table of contents is derived from the
  level-2 headings at request time.
- Screenshots are served from app/static/help/screenshots/ (32 images).
- Regenerate after editing the manual:
    documentatie/convert_help_page.sh
    docker compose up -d --build

Also adds
- backup_players_playlists.sh / restore_database.sh for DB backup and restore.
- .gitignore rules so local database backups (real production data), generated
  .docx files and duplicate screenshot copies are never committed.

.gitignore

@@ -76,6 +76,27 @@ build/
 #data
 data/
 
+# Local database backups / restore points.
+# These contain REAL production data (users, password hashes, player feedback).
+# They must never leave the host — keep them on disk only.
+backups/
+restore-points/
+
+# Generated documents (regenerate with documentatie/convert_manual.sh)
+documentatie/*.docx
+
+# Screenshots are shipped with the app under app/static/help/screenshots/.
+# The copy in documentatie/ is the editing source; ignore it to avoid committing
+# ~4 MB twice.
+documentatie/screenshots/
+
+# Local notes / scratch files
+inportant info .txt
+important info.txt
+
+# Legacy pre-sanitization archive (also covered as docs/old_code_documentation/)
+old_code_documentation/
+
 # Local archive / restore-point snapshots.
 # Kept on disk for reference (see docs/SANITIZATION-REVIEW.md) but deliberately
 # NOT tracked: docs/legacy code/ is a full pre-sanitization repo snapshot and