Refactor Cloudflare worker runtime names to use Amby-prefixed entities

[punitarani]

Summary

• Rename Durable Object and Workflow classes to Amby* names and switch worker exports to the renamed entities
• Update Wrangler bindings, workflow names, and destructive DO migrations to use AMBY_* bindings and Amby-prefixed runtime classes
• Propagate the new binding names through worker/env types, Telegram routing, sandbox provisioning, and runtime observability strings
• Refresh runtime and Telegram attachment docs to match the renamed Cloudflare surface

Testing

• Not run (not requested)