[Sub-Issue] Implement FlixelTextBox (full keyboard support)

[stringdotjar]

A robust text input field for user entry.

Requirements:

• Support for all standard keyboard shortcuts (Ctrl+C, Ctrl+V, Ctrl+A, Ctrl+Z, Ctrl+Left/Right, etc.). THIS IS MANDATORY.
• Caret blinking and text selection highlighting.
• Multi-line support (toggleable).
• Input filtering (numeric only, alphanumeric, etc.).