Add comprehensive --help documentation and --version flag

[SL-Mar]

Feature Implementation

Implements the feature request for a built-in --help command to improve CLI usability.

Changes Made

1. Enhanced Main Help

   • Comprehensive description of QuantCoder's purpose
   • Step-by-step workflow guide (search → list → download → summarize → generate)
   • Practical usage examples
   • Highlights interactive mode for new users

2. Added --version Flag

   • Shows CLI version (v0.3)
   • Displays OpenAI SDK version (important for v0.28 compatibility)

3. Improved Command Descriptions

   • Clear parameter explanations
   • Usage examples for each command
   • Prerequisites noted (e.g., "must download first")
   • Consistent formatting across all commands

Example Usage

quantcli --help                  # Main help with workflow
quantcli --version               # Version information
quantcli search --help           # Command-specific help
quantcli generate-code --help    # Another example

Benefits

✅ Improves accessibility for new users
✅ Reduces dependency on external documentation
✅ Self-documenting CLI interface
✅ Shows typical workflow clearly
✅ Backward compatible (no breaking changes)

Testing

All existing commands remain functional. Help text is now comprehensive and informative.

Closes issue requesting --help / -h command functionality.