Basic inline formula editing

[ruippgoncalves]

This PR introduces several foundational features aimed at improving the formula editing experience:

• Introduced a basic on-screen keyboard to allow formula editing directly inline
• Built a structured internal representation of formulas
• Operator precedence works naturally without the need for users to input parentheses manually
• It also lays the groundwork for potential SVG or canvas-based rendering in the future
• Adjusted the symbol layout and interactions to be more accessible and comfortable for touch input

I must say:

• I’m not entirely sure this aligns 100% with the intended direction of the project, so please feel free to push back or redirect if needed
• The code isn’t commented yet since I prioritized getting a working structure in place first
• This is quite a substantial PR, but I’m happy to break it down or rework parts based on your feedback

Looking forward to your thoughts!

[dchahla]

This looks really good! I would love to...

1. Up / down and or left / right arrows working to walk through the function.
2. Keep the textual input available for direct editing.
3. Retain the CSS