refactor: standardize all media renderers

[najuna-brian]

Description

This PR standardizes all media renderers with a consistent, responsive icon-first pattern.
Closes #102

Changes implemented

Standardized pattern across all media renderers:

1. Empty state (action-first):

• Medium-sized IconButton: 56px on phones, 64px on tablets
• Icon size: 28px on phones, 32px on tablets
• Centered layout with minimal text
• Responsive using MUI breakpoints (xs, sm)

2. After capture (preview + actions):

• Preview displayed prominently
• Small IconButtons for retry/delete actions
• Consistent spacing and alignment

3. Modern sizing:

• Replaced 80x80 buttons and 40–48px icons
• Uses MUI's size="large" for primary actions
• Icons sized with responsive fontSize prop

Updated renderers:

PhotoQuestionRenderer — Icon-first capture button
AudioQuestionRenderer — Consistent icon sizing (was 80x80)
VideoQuestionRenderer — Icon-first pattern with icon controls
FileQuestionRenderer — Icon-first file selection
SignatureQuestionRenderer — Icon-first signature capture
GPSQuestionRenderer — Icon-first GPS capture

Benefits:

1. Mobile-first: Touch-friendly sizes (56–64px buttons)
2. Responsive: Adapts to phones and tablets
3. Consistent: Same pattern across all media types
4. Modern: Appropriate icon sizes (28–32px)
5. Accessible: Proper aria-label attributes
6. Clean: Simplified UI with less text

All renderers now follow the same pattern, making the UX consistent and mobile-friendly.

Screenshots

[r0ssing]

Looks great! Let's do a new Formulus release soon that includes this :-) 🦒