Add autosave feature

[v8vito]

Resolves #29

Problem

Notes were not saved automatically to the persistence file, resulting in potential loss of information if VSCode exited unexpectedly.

Solution

• Persist the local database immediately whenever saveNoteComment runs, so file autosaves after every new note, reply, or status change.
• After syncing remote state (syncNoteMapWithRemote) or receiving remote updates via RethinkDB subscriptions, write the updated note map to disk to keep local and collaborative data aligned.
• Remove the helper dependency in utils/index.ts by reading the security-notes.localDatabase setting directly from the VS Code configuration, avoiding circular imports.