feat(dictionary): add Hachidori backend support

- Add backend selection, setup gating, Anki integration, and external host support
- Add launcher flags, documentation, packaging, and focused tests
- Open on-demand overlay modals on the first attempt

src/main/runtime/cli-command-context-factory.test.ts

@@ -74,6 +74,7 @@ test('cli command context factory composes main deps and context handlers', () =
     runUpdateCommand: async () => {},
     runEnsureLinuxRuntimePluginAssetsCommand: async () => {},
     runYoutubePlaybackFlow: async () => {},
+    openHachidoriSettings: () => {},
     openYomitanSettings: () => {},
     openConfigSettingsWindow: () => {},
     openSyncUiWindow: () => {},