feat(forms): add public form access and response submission for participants

- Implemented public access to forms with `getPublic` procedure.
- Added `submitPublic` procedure for participants to submit responses.
- Created a new participant form page to handle form display and submission.
- Enhanced form validation and error handling for required fields.
- Introduced CSV export functionality for form responses.
- Updated form listing and template creation procedures.
- Added README for homepage screenshots.

public/images/screenshots/README.md

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+# Homepage Screenshots
+
+Add your app screenshots here. The homepage will display them automatically.
+
+## Required Screenshots
+
+1. **experiment-designer.png** - Visual experiment designer showing block-based workflow
+2. **wizard-interface.png** - Wizard execution interface with trial controls
+3. **dashboard.png** - Study dashboard showing experiments and trials
+
+## Recommended Size
+
+- Width: 1200px
+- Format: PNG or WebP
+- Quality: High (screenshot at 2x for retina displays)
+
+## Preview in Browser
+
+After adding screenshots, uncomment the `<Image>` component in `src/app/page.tsx`:
+
+```tsx
+<Image
+  src={screenshot.src}
+  alt={screenshot.alt}
+  fill
+  className="object-cover transition-transform group-hover:scale-105"
+/>
+```