feat(settings): add Mouse & Touchpad settings tab for Niri (#2905)

* feat(settings): add Mouse & Trackpad settings tab

* style(settings): clarify touchpad natural scroll description

* chore(settings): update settings search index

* refactor(settings): unify Mouse & Trackpad terminology to Mouse & Touchpad

* feat(setup): deploy default dms/input.kdl on setup

* style(niri): restore include section comment in base config template

* refactor(niri): remove redundant input block from base config template

* refactor(niri): restore keyboard and non-mouse input config to base template

* feat(settings): add touchpad disable-on-external-mouse toggle

* feat(settings): add left-handed, scroll-factor and dwt options

* feat(settings): add middle-emulation, scroll-method, tap-and-drag and drag-lock options

* refactor(settings): re-order mouse and touchpad UI options logically

quickshell/translations/settings_search_index.json

@@ -9916,5 +9916,18 @@
       "widgets"
     ],
     "icon": "dashboard"
+  },
+  {
+    "section": "_tab_44",
+    "label": "Mouse & Touchpad",
+    "tabIndex": 44,
+    "category": "Settings",
+    "keywords": [
+      "mouse",
+      "settings",
+      "touchpad"
+    ],
+    "icon": "mouse",
+    "conditionKey": "isNiri"
   }
 ]