#27 issue solved-------Feature/chat history export

[dikshantbhangala]

#27 Done with solving issue

• Added Export Functionality: Enabled chat export as PDF and JSON with options for embedded or separate media files.
• Database Integration: Implemented SQLite support for storing messages and media paths locally.
• Encryption Handling: Enhanced RSA decryption with error handling and proper key usage.
• UI Improvements: Grouped messages by date, improved message bubbles, and added a file preview feature.
• Code Refactoring: Optimized message retrieval, export logic, and error handling for better performance.

[dikshantbhangala]

@bhavik-mangla done with the merging in main branch as you told. And the video part i will provide shortly

[bhavik-mangla]

Please follow the contribution guidelines
https://github.com/AOSSIE-Org/OpenPeerChat-flutter/blob/main/Contribution_Guidelines.md