fix(offline): pre-cache home README under its synthetic key

The home page reads README via getCachedMainReadme, which uses
Note-{owner}-{repo}-README, not the blob SHA. Cache-all only wrote
SHA-keyed entries, so the homepage README was empty offline.

src/hooks/useOfflineNotes.hook.ts

@@ -5,7 +5,7 @@ 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"
-import { queryFileContent } from "@/modules/repo/services/repo"
+import { getMainReadme, queryFileContent } from "@/modules/repo/services/repo"
 import { useUserRepoStore } from "@/modules/repo/store/userRepo.store"
 
 export const useOfflineNotes = () => {
@@ -58,6 +58,12 @@ export const useOfflineNotes = () => {
 
       saveCacheNote(contentFile)
     }
+
+    try {
+      await getMainReadme(store.user, store.repo)
+    } catch {
+      failedNotes.value++
+    }
   }
   const { execute, isLoading } = useAsyncState(cacheAllNotes, null, {
     immediate: false