feat: add chat history backup and restore functionality

[sidbetatester]

This PR adds chat history backup and restore functionality, continuing the work from #280.

Changes include:

• Enhanced chat import with support for multiple formats:
  • Standard Bolt format
  • Chrome extension IndexedDB backup format
  • History array format
• Improved validation and error handling
• Added user feedback via toast notifications
• Updated README to reflect the new feature

Note: After the #280 commits, the structure of bolt has significantly changed, so in this commit, I only introduced what you missed including from my previous commit and must not have any conflicts.

Previous feedback addressed:

1. Fixed TypeScript issues
2. Improved error handling and validation
3. Added proper success messages
4. Cleaned up code organization

Reference: This continues the work from #280 which was accidentally closed during branch reorganization.
#280

[sidbetatester]

Hi Anirban @thecodacus
I cleaned up the code to match latest version, we should not have any conflicts now. Can you verify and approve.

[thecodacus]

Hi Anirban @thecodacus I cleaned up the code to match latest version, we should not have any conflicts now. Can you verify and approve.

I have added my reviews. I just noticed that you are using your main branch to raise PR, Please read the contribution guidelines here , and use a feature branch for the PR. else any changes to your main will automatically be reflected to this PR which can be problematic.

[sidbetatester]

Hi Anirban @thecodacus I cleaned up the code to match latest version, we should not have any conflicts now. Can you verify and approve.

I have added my reviews. I just noticed that you are using your main branch to raise PR, Please read the contribution guidelines here , and use a feature branch for the PR. else any changes to your main will automatically be reflected to this PR which can be problematic.

thank you, acknowledged, I did follow the CONTRIBUTING.md the first time, should have remembered to do that same. I was using windsurf for my edits and commits.