devx: web2-friendly APIs (service bus/webhooks/REST)

[TheNewAutonomy]

Goal

Make Catalyst easy to integrate for web2 developers without requiring deep JSON-RPC expertise.

Scope

• Review current integration surfaces:
  • JSON-RPC
  • service bus (websocket/webhooks)
• Define recommended integration patterns:
  • webhooks for transfers/contract events
  • REST facade for common queries
  • auth/rate limits
• Provide reference SDKs/snippets and sample apps

Acceptance criteria

• A web2 developer can build a basic app (balances + transfers + event subscriptions) with minimal blockchain knowledge
• Documented, stable APIs exist for the recommended path

Refs: crates/catalyst-service-bus, #187 (RPC epic), #206 (runbook).