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/composers/cli-startup-composer.test.ts

@@ -50,6 +50,7 @@ test('composeCliStartupHandlers returns callable CLI startup handlers', () => {
       runUpdateCommand: async () => {},
       runEnsureLinuxRuntimePluginAssetsCommand: async () => {},
       runYoutubePlaybackFlow: async () => {},
+      openHachidoriSettings: () => {},
       openYomitanSettings: () => {},
       openConfigSettingsWindow: () => {},
       openSyncUiWindow: () => {},