bettter persistence

[ForestMars]

Context

Following on the recently added a "Private" checkbox (allowing users to mark individual messages as ephemeral/session-only) which is implemented by ChatInterface.tsx skiping calling conversation State.addMessage() for private messages, preventing them from being saved.
However, relying solely on UI-layer filtering is fragile : bugs, refactoring, or edge cases could cause private messages to leak into the persistence layer.

Problem

Private messages (marked with isPrivate: true) must NEVER be persisted to IndexedDB or synced to the server. They should only exist in app state during the current session and disappear on refresh.

Solution

Implement defense-in-depth filtering at the persistence layer to guarantee private messages are never saved, regardless of what happens upstream.

Changes Made

src/services/indexedDbStorage.ts

1. Filter private messages before saving (prepareChatForStorage())

• Added filteredMessages array that strips out any message where isPrivate === true
• Applied to all persistence operations (local IndexedDB + server sync)

2. Auto-cleanup empty conversations (saveConversation())
   If filtering results in zero messages (all were private), delete the conversation from:

• Local IndexedDB (this.db.chats.delete())
• Remote server (DELETE /deleteChat/:id)

Prevents empty conversations from cluttering the sidebar 🚀!!!

Expected Behavior

• Private messages: Never saved to IndexedDB, never synced to server, disappear on page refresh
• Conversations with only private messages: Automatically deleted from sidebar
• Mixed conversations: Private messages filtered out, non-private messages persist normally

Architecture

Two-layer defense:

• UI Layer (ChatInterface.tsx): Skips addMessage() for private messages
• Persistence Layer (this PR): Filters private messages as safety net

NB: PR addresses multiple issues

• updates CI/CD from npm to bun
• This PR also adds 102 lines of unit tests for MCP service (unrelated to private messages)
  src/__tests__/services/mcpService.test.ts

[ForestMars]

Let's merge this in to reduce the diff on #52