feat: improve note organization and search

[saurabh-911]

Summary

This PR implements a Python 3.11 AI Coding Agent and demonstrates its capabilities by improving the target Node.js application.

AI Coding Agent

The agent is implemented under the agent/ directory and performs the following workflow:

• Repository exploration
• Automatic project analysis
• Execution planning
• LLM-driven code generation
• Validation
• Change summarization

Architecture:

Explorer
↓
Planner
↓
Executor
↓
Validator
↓
Summarizer

Product Requirement Implemented

To demonstrate the agent, it implemented:

• Tag support for notes
• Search by keyword
• Tag-based filtering
• Request validation improvements
• Documentation updates

Technical Notes

• The Node.js application remains the target application.
• The AI agent is implemented separately in Python 3.11+ under the agent/ directory.
• The design uses an LLMClient abstraction to support different LLM providers.