Platform: Projects page — move create form to Dialog, add search, fix links

[8dazo]

Summary

Improve the projects list page by moving the always-visible create form into a Dialog, adding search/filter, and replacing text-only links with proper Button components.

Current Defect

• Create form occupies 380px permanently — wastes space after projects exist
• No search or filtering on project cards
• "Back to project" text link is plain text-cyan-300 — not a Button
• Card hover effects use hardcoded border-cyan-400/40 instead of semantic tokens
• Success/error feedback uses inline <p> tags instead of toasts

Solution

• Move ProjectCreateForm into a <Dialog> triggered by a "New Project" CTA Button
• Add search Input above project cards grid
• Replace text-cyan-300 links with <Button variant="outline" asChild><Link>
• Card hover: hover:border-primary/40 instead of hover:border-cyan-400/40
• Add Sonner toasts for create success/error in ProjectCreateForm

Files to Modify

• Modify: apps/platform/app/projects/page.tsx
• Modify: apps/platform/components/project-create-form.tsx

Acceptance Criteria

• Create form is in a Dialog, triggered by CTA button
• Search input filters project cards
• All links use Button variant="outline" asChild+Link pattern
• Card hover uses semantic tokens
• Create success/error uses Sonner toasts

Depends on #95, #96
Part of #dashboard-ui-modernization