perf: move PouchDB/IndexedDB operations to a Web Worker

All database reads and writes now run off the main thread via a
dedicated worker, eliminating IndexedDB overhead from the frame budget.

- Create data.worker.ts exposing the Data class via Comlink
- Refactor data.ts to export a Comlink-wrapped proxy and a standalone
  generateId() pure function (workers can't expose sync methods cleanly)
- Update all 10 call sites to import generateId directly instead of
  calling data.generateId()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/hooks/useOfflineNotes.hook.ts

@@ -1,7 +1,7 @@
 import { useAsyncState } from "@vueuse/core"
 import { computed, ref } from "vue"
 
-import { data } from "@/data/data"
+import { data, generateId } from "@/data/data"
 import { DataType } from "@/data/DataType.enum"
 import { prepareNoteCache } from "@/modules/note/cache/prepareNoteCache"
 import { Note } from "@/modules/note/models/Note"
@@ -36,7 +36,7 @@ export const useOfflineNotes = () => {
 
       if (
         !file.sha ||
-        cachedNotesSet.has(data.generateId(DataType.Note, file.sha))
+        cachedNotesSet.has(generateId(DataType.Note, file.sha))
       ) {
         continue
       }