feat: optimize canvas load and save using lazy loading and delta upserts

fix: treat null/empty SubscriptionTier as Free tier in all limit checks

Implement custom templates and subscription tiers backend changes

Optimize prompts for recursive roadmap generation and add goal templates

fix: resolve EF Core Edge mapping GraphId ForeignKey constraint violation in SaveFullGraphAsync

fix: refactor Edge.Condition to string for precise handle-based connection persistence

Extend TaskNode with visual and data fields to support images, drawing and custom text

fix: allow collaborators to get graph shares and prepend graph owner to list of collaborators

init