feat: Error Handling & UX Polish

[pasogott]

User Story: As a user, I want helpful error messages, so that I can fix issues quickly.

Tasks

• Review all error messages for clarity
• Add suggestions to error messages
• Implement better progress indicators
• Add colors and formatting with Rich
• Handle interrupts gracefully (Ctrl+C)
• Add --debug flag for verbose output
• Test UX with fresh eyes
• Write UX guidelines doc

Acceptance Criteria

• Error messages explain what went wrong and how to fix
• Progress bars work for long operations
• Colors enhance readability
• Ctrl+C stops gracefully without tracebacks
• --debug shows detailed logs

Files to Update

• All command files (error messages)
• src/frappecli/cli.py (debug flag)
• docs/contributing.md (UX guidelines)

Phase: 5 | User Story: 5.3