feat: yoloVisibility config, alwaysShowLabel on groups, site settings panel

- AppConfig gains yoloVisibility: 'auto' | 'never' (default: auto)
- Group gains alwaysShowLabel?: boolean
- YOLO toggle only renders when showYoloToggle is true (auto + >1 group)
- Group divider shows when >1 group OR alwaysShowLabel is set
- New /admin/api/config GET+PUT endpoint for yolo settings
- Admin: alwaysShowLabel checkbox in group form
- Admin: ⚙ Settings panel with YOLO label, description, and visibility controls

data/units.json

@@ -1,14 +1,5 @@
 {
   "units": [
-    {
-      "id": "pound",
-      "label": "pound",
-      "labelPlural": "pounds",
-      "symbol": "lb",
-      "group": "dickloads",
-      "toBase": 0.038,
-      "description": "My description is {dickload:description}"
-    },
     {
       "id": "dickload",
       "label": "dickload",
@@ -18,6 +9,15 @@
       "toBase": 1,
       "description": "See {pound:description}"
     },
+    {
+      "id": "pound",
+      "label": "pound",
+      "labelPlural": "pounds",
+      "symbol": "lb",
+      "group": "dickloads",
+      "toBase": 0.038,
+      "description": "My description is {dickload:description}"
+    },
     {
       "id": "barrel",
       "label": "barrel",
@@ -92,12 +92,30 @@
       "symbol": "shttn",
       "group": "dickloads",
       "toBase": 38
+    },
+    {
+      "id": "asdf",
+      "label": "asdf",
+      "labelPlural": "asdf",
+      "symbol": "asdf",
+      "group": "another-group",
+      "toBase": 1,
+      "hidden": true
     }
   ],
   "groups": [
     {
       "id": "dickloads",
-      "label": "Dickloads",
+      "label": "Weights and Masses",
+      "baseUnitId": "",
+      "toUniversal": 1,
+      "sortOrder": "alpha",
+      "hidden": false,
+      "alwaysShowLabel": true
+    },
+    {
+      "id": "another-group",
+      "label": "Another Group",
       "baseUnitId": "",
       "toUniversal": 1
     }