Migrate frontend services to support translations (#96342)

Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>

homeassistant/components/frontend/services.yaml

@@ -1,29 +1,19 @@
 # Describes the format for available frontend services
 
 set_theme:
-  name: Set theme
-  description: Set a theme unless the client selected per-device theme.
   fields:
     name:
-      name: Theme
-      description: Name of a predefined theme
       required: true
       example: "default"
       selector:
         theme:
           include_default: true
     mode:
-      name: Mode
-      description: The mode the theme is for.
       default: "light"
       selector:
         select:
           options:
-            - label: "Dark"
-              value: "dark"
-            - label: "Light"
-              value: "light"
-
+            - "dark"
+            - "light"
+          translation_key: mode
 reload_themes:
-  name: Reload themes
-  description: Reload themes from YAML configuration.

homeassistant/components/frontend/strings.json

@@ -0,0 +1,30 @@
+{
+  "services": {
+    "set_theme": {
+      "name": "Set the default theme",
+      "description": "Sets the default theme Home Assistant uses. Can be overridden by a user.",
+      "fields": {
+        "name": {
+          "name": "Theme",
+          "description": "Name of a theme."
+        },
+        "mode": {
+          "name": "Mode",
+          "description": "Theme mode."
+        }
+      }
+    },
+    "reload_themes": {
+      "name": "Reload themes",
+      "description": "Reloads themes from the YAML-configuration."
+    }
+  },
+  "selector": {
+    "mode": {
+      "options": {
+        "dark": "Dark",
+        "light": "Light"
+      }
+    }
+  }
+}