feat: add weblink playlists, SSH player deployment, Caddy HTTPS, build player page

- Content model: add url column + is_weblink() for web page content items
- Player model: add deployment tracking fields (status, timestamps, message)
- Content blueprint: add add_weblink and add_weblink_to_playlist routes;
  weblinks auto-deleted when removed from playlist
- Players blueprint: add SSH deploy mode in add_player; weblink-aware playlist
- API blueprint: weblink URL served directly in playlist response;
  add /api/deploy/test-ssh and /api/deploy/player endpoints
- Admin blueprint: add build-player page (clone from Gitea, write base config);
  replace nginx status card with Caddy status on HTTPS config page
- caddy_manager: rewritten to generate proper HTTPS/internal-CA Caddyfiles
  and reload Caddy via admin API (/load) for live config updates
- ssh_deploy, background_tasks, player_build: new utils for SSH deployment
- background_tasks: push Flask app context into background thread so DB
  updates after deployment complete correctly
- ssh_deploy: robust install script detection with passwordless sudo injection
  (uses SSH credentials, cleaned up after install)
- Dockerfile: add git, sshpass, openssh-client, rsync
- docker-compose: switch nginx to Caddy on ports 80/443; add port 5000 for dev
- Templates: add_player deploy mode UI, weblink form in playlist/upload pages,
  build_player admin page, Caddy status on HTTPS config page
- Migrations: add_url_to_content, add_deployment_fields_to_player
- app.py: call db.create_all() on startup for schema bootstrap
- config.py: add PLAYER_CODE_DIR and PLAYER_REPO_URL settings

app/utils/script_name_fix.py

@@ -0,0 +1,26 @@
+"""
+ScriptNameFix WSGI middleware.
+
+When nginx strips the path prefix before forwarding to a Flask app it also
+sets the X-Script-Name header (e.g. /digiserver).  This middleware reads
+that header and sets SCRIPT_NAME in the WSGI environ so that Flask's
+url_for() generates absolute URLs with the correct prefix.
+
+Usage in the app factory:
+    from app.utils.script_name_fix import ScriptNameFix
+    app.wsgi_app = ScriptNameFix(app.wsgi_app)
+"""
+
+
+class ScriptNameFix:
+    def __init__(self, app):
+        self.app = app
+
+    def __call__(self, environ, start_response):
+        script_name = environ.get('HTTP_X_SCRIPT_NAME', '').rstrip('/')
+        if script_name:
+            environ['SCRIPT_NAME'] = script_name
+            path_info = environ.get('PATH_INFO', '/')
+            if path_info.startswith(script_name):
+                environ['PATH_INFO'] = path_info[len(script_name):] or '/'
+        return self.app(environ, start_response)