feat: improve forms examples with bento grid, column layouts, and wizard styling

[mmcintosh]

Description

Overhaul the Forms Examples page (/admin/forms/examples) with a modern bento card grid layout, proper column-based form layouts, and full wizard step navigation styling.

This is a companion to PR #623 (Forms as Collections) — #623 adds the backend feature, this PR polishes the visual showcase.

Changes

Bento Card Grid Landing

• Replace sidebar navigation with responsive 3-column bento card grid
• Cards grouped by category (Getting Started, Advanced, Components)
• Featured cards span 2 columns; responsive breakpoints at 1024px and 640px
• Click-to-expand detail view with back navigation and hash routing

Form.io CSS Fixes

• Add formio.full.min.css stylesheet (was missing on examples page)
• Restore Bootstrap grid CSS (.row, .col-* flex rules) scoped to .example-demo
• Restore Bootstrap pagination for wizard step tabs (.pagination, .page-item, .page-link)
• Comprehensive Form.io input/label/button styling matching builder page patterns
• Wizard button styling: next = blue, submit = green
• Mobile responsive: columns stack to single below 640px

Column Layouts (Form.io columns component)

• Kitchen Sink: firstName+lastName, email+phone, appointmentDateTime+birthDate, country+interests, checkbox+terms
• Contact: name+email side-by-side, message full-width
• Thank You: firstName+lastName, email+phone side-by-side
• Address: city+state side-by-side, street and zip full-width
• File Upload: name+email side-by-side

New Multi-Page Wizard Example

• Classic 3-step registration wizard (Personal Info → Contact → Preferences)
• Column layouts in each step
• Dedicated bento card and JSON code block

Updated JSON Code Blocks

• Kitchen Sink, Contact, Thank You snippets updated to show column-based schemas

Testing

Unit Tests

• All unit tests passing (1266 tests)

E2E Tests

• All E2E tests passing (template-only change, no new E2E needed)
• Deployed to preview and manually verified:
  • Column layouts render side-by-side on all forms
  • Wizard step tabs styled with proper pagination
  • Mobile responsive stacking works
  • All forms still function (inputs, validation, submit)

Screenshots/Videos

Checklist

• Code follows project conventions
• Tests added/updated and passing
• Type checking passes
• No console errors or warnings
• Documentation updated (if needed)

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