feat(notes): add completed task cleanup controls

[antonreshetov]

Summary

• add notes task cleanup API and markdown storage support for completed tasks
• add preferences and menu controls for hiding and cleaning up completed tasks
• cover cleanup and main-menu context behavior with focused tests

Validation

• pnpm api:generate
• pnpm i18n:copy
• pnpm test src/main/menu/tests/main.test.ts src/renderer/composables/spaces/notes/tests/useNotes.test.ts src/renderer/ipc/main-menu/tests/context.test.ts src/main/storage/providers/markdown/notes/storages/tests/notes.test.ts
• pnpm -s eslint src/main/api/dto/notes.ts src/main/api/routes/notes.ts src/main/index.ts src/main/menu/tests/main.test.ts src/main/menu/main.ts src/main/storage/contracts.ts src/main/storage/providers/markdown/notes/storages/notes.ts src/main/store/module/app.ts src/main/store/module/preferences.ts src/main/store/types/index.ts src/main/tasks.ts src/main/types/ipc.ts src/main/types/menu.ts src/renderer/components/notes/NotesSidebarLibrary.vue src/renderer/components/preferences/NotesEditor.vue src/renderer/composables/spaces/notes/tests/useNotes.test.ts src/renderer/composables/spaces/notes/useNotes.ts src/renderer/composables/spaces/notes/useNotesApp.ts src/renderer/ipc/listeners/main-menu.ts src/renderer/ipc/main-menu/tests/context.test.ts src/renderer/ipc/main-menu/context.ts src/renderer/ipc/main-menu/sync.ts src/renderer/services/api/generated/index.ts

Note: pnpm i18n:check currently fails on existing missing keys across non-en/ru locales.