fix: Prevent multi-line titles and descriptions across commands

[DylanDevelops]

Pull Request Checklist

• I have read and followed the contribution guidelines.
• My pull request targets the main branch of tmpo.
• I have tested these changes locally on my machine.

Description

This pull request introduces a new utility function for input sanitization and consistently applies it across several commands to ensure user inputs are single-line, trimmed, and free of line breaks. The update improves input handling and prevents multi-line or malformed strings from being inadvertently processed. Comprehensive unit tests are also added to verify the correctness of the new sanitization logic.

Input sanitization improvements:

• Added a new function SanitizeSingleLine in internal/ui/ui.go that replaces all newline and carriage return characters in a string with spaces and trims leading/trailing whitespace.
• Replaced previous strings.TrimSpace calls with ui.SanitizeSingleLine for user inputs in cmd/entries/edit.go, cmd/entries/manual.go, cmd/milestones/start.go, and cmd/tracking/start.go to ensure consistent single-line input handling. [1] [2] [3] [4] [5]

Testing enhancements:

• Added a comprehensive set of unit tests for SanitizeSingleLine in internal/ui/ui_test.go to cover various edge cases, including different types of whitespace and line breaks.

Dependency updates:

• Imported the strings package in internal/ui/ui.go to support the new sanitization function.