feat: add layout switching and vertical links layout

[jojo58fr]

Description

This PR adds a full layout switching system to the builder with support for a new Vertical Links Layout alongside the existing Bento layout.

It includes:

• a layout switcher in the top toolbar next to the preview mode controls
• a layout selection modal with a warning that switching layout resets the arrangement
• persisted layout selection through pageLayout
• support for the selected layout in the builder, preview page, and export templates
• a dedicated Vertical Links Layout with stacked blocks and profile header editing parity
• vertical drag and drop reordering, including long-press drag support
• a new vertical-only Collection block with:
  • title
  • expanded/collapsed by default setting
  • animated open/close behavior
  • drag/drop support to move blocks into and out of collections
• cleanup of vertical-only blocks when switching back from Vertical Links Layout to Bento
• documentation for the full layout switching implementation

This PR also fixes type-check issues that were blocking validation and updates related typing for analytics and social platform icons.

Related Issue

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🎨 Style/UI improvement
• ♻️ Code refactoring (no functional changes)
• ⚡ Performance improvement
• 🔧 Configuration/build changes

Checklist

• My code follows the project's code style
• I have run npm run lint and fixed any issues
• I have run npm run format to format my code
• I have run npm run type-check with no errors
• I have tested my changes locally with npm run dev
• I have added/updated documentation if needed
• My changes generate no new warnings

Screenshots (if applicable)

Additional Notes

Documentation was added in docs/usage/layout-switching.md.