UI tweaks (#23492)

* slightly darken bg-card

* change menu label

* move snapshot retain out of advanced fields

* add new ui options for collapsibles

* backend title and description

* remove unused snapshot retention field

* update reference config

* remove further references to snapshots retain.mode

web/public/locales/en/config/cameras.json

@@ -152,8 +152,8 @@
     }
   },
   "ffmpeg": {
-    "label": "FFmpeg",
-    "description": "FFmpeg settings including binary path, args, hwaccel options, and per-role output args.",
+    "label": "Streams (FFmpeg)",
+    "description": "Camera stream inputs and FFmpeg options, including binary path, args, hwaccel, and per-role output args.",
     "path": {
       "label": "FFmpeg path",
       "description": "Path to the FFmpeg binary to use or a version alias (\"7.0\" or \"8.0\")."
@@ -666,10 +666,6 @@
         "label": "Default retention",
         "description": "Default number of days to retain snapshots."
       },
-      "mode": {
-        "label": "Retention mode",
-        "description": "Mode for retention: all (save all segments), motion (save segments with motion), or active_objects (save segments with active objects)."
-      },
       "objects": {
         "label": "Object retention",
         "description": "Per-object overrides for snapshot retention days."