Each user gets their own IDB database (keepnotes-{userId}), preventing
data leaks between users on the same device. Add initDb(userId) called
on mount and destroyDb() for logout cleanup.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- Bump IDB version to 2, add pendingAttachments object store with noteId index
- Add CRUD helpers: addPendingAttachment, getPendingAttachments, removePendingAttachment
- ImageUpload stores blobs in IDB when offline, displays via blob URLs
- Show pending sync indicator (RefreshCw icon) on not-yet-uploaded images
- Add pushPendingAttachments to sync client, runs after note push
- Pending attachments auto-upload on reconnect via existing online event listener
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
