Add read-only external Yomitan profile support

- add `yomitan.externalProfilePath` config and default/template wiring
- load Yomitan from an external Electron profile/session when configured
- disable SubMiner Yomitan writes/settings UI in external-profile mode and update docs/tests

src/config/definitions/template-sections.ts

@@ -127,6 +127,15 @@ const INTEGRATION_TEMPLATE_SECTIONS: ConfigTemplateSection[] = [
     ],
     key: 'anilist',
   },
+  {
+    title: 'Yomitan',
+    description: [
+      'Optional external Yomitan profile integration.',
+      'Setting yomitan.externalProfilePath switches SubMiner to read-only external-profile mode.',
+      'In external-profile mode SubMiner will not import, delete, or modify Yomitan dictionaries/settings.',
+    ],
+    key: 'yomitan',
+  },
   {
     title: 'Jellyfin',
     description: [