[Cloud Service] Add account sync backend (bookmarks + notes)

[jacksonw111]

Goal

Support cross-device sync for user data.

Scope

• Add Drizzle schema/tables for bookmark sync and note sync
• Implement typed RPC procedures:
  • list sync payload
  • upsert bookmark
  • delete bookmark
  • upsert note
  • delete note
• Scope all records by authenticated user id

Acceptance Criteria

• Authenticated users can create/read/update/delete their own bookmarks and notes
• Users cannot read or mutate other users data
• Typecheck and build pass