Enhancement: Add per-Lanyard custom open graph images and metadata

[renderghost]

Description

Allow users to customize Open Graph images and metadata for their individual Lanyard profile, enabling personalized social sharing previews.

Current State

• Default Open Graph image for all pages (/og/default.png)
• Generic metadata for all profiles

Proposed Features

Custom OG Image Options

1. Auto-generated: Create OG image from profile data
   • Profile photo
   • Name and title
   • Institution/affiliation
   • Branded Lanyards template
2. User upload: Allow custom 1200x630 image upload
3. Template selection: Choose from predefined templates

Custom Metadata

• Custom title (default: "[Name] - Lanyards")
• Custom description (default: bio/description)
• Keywords/tags for SEO

Implementation

1. Add OG image field to profile settings
2. Create image generation service:
   • Use Canvas API or similar (server-side)
   • Template with profile data
   • Cache generated images
3. Update profile metadata endpoint
4. Generate dynamic <meta> tags per profile
5. Store custom images in user's PDS or cloud storage

Technical Considerations

• Image optimization and caching
• Storage location (PDS vs CDN)
• Generation performance
• Default fallbacks

Benefits

• Personalized social sharing
• Better click-through rates
• Professional appearance
• Brand consistency for institutions

Priority

Medium - Nice enhancement for sharing and discovery