Add settings page tabs and show env API keys with last four digits.

System settings now use the same CSS tab layout as env config; sensitive env fields display masked values from .env while keeping save-on-empty behavior.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/instance/instance_settings_register.py

@@ -168,6 +168,7 @@ def merge_ui_template_context(page: str, get_db: Callable, **settings_kwargs: An
     prefs = get_display_prefs(get_db)
     ctx = {
         "display": prefs,
-        **settings_page_context(page, **settings_kwargs),
+        "display_meta": display_meta_for_ui(),
+        **settings_page_context(page, display=prefs, **settings_kwargs),
     }
     return ctx