[P3] AI-generated custom event images

[KalebCole]

Priority: P3 (Lower)

Generate custom event images/flyers using AI.

Concept

# Generate flyer with AI
partiful create --title "Beach Day" --generate-image "beach sunset party vibes"

# Generate and preview before using
partiful image generate "game night retro arcade style" --preview
partiful create --title "Game Night" --image ./generated.png

Implementation Options

1. DALL-E / Midjourney API - generate from prompt
2. Canva API - template-based generation
3. Local Stable Diffusion - if user has it set up

Dependencies

• Requires [P2] Event images - built-in posters and custom upload #5 (custom image upload) to be implemented first
• Needs API key for image generation service

Scope

This is nice-to-have. Most users will be fine with Partiful's built-in posters.

Acceptance Criteria

• Generate image from text prompt
• Preview before using
• Multiple style options
• Reasonable generation time (<30s)