feat(api): POST /api/v2/workflows/[id]/execute

Thin route over executeWorkflowService: X-API-Key or anonymous
public-API auth (sync/stream only for anonymous), strict body with
body-flag async (no mode headers on v2), SSE passthrough for stream,
and the execution resource response — executionId always present,
in-band run failures are status:'failed' with the structured
{message, code, blockId, blockName, blockType} error, sync timeout is
status:'failed' + TIMEOUT instead of v1's 408, and a Response block's
payload stays inside output (authors never control response
status/headers on this origin). Async debits the async bucket and the
202 statusUrl points at the v2 executions resource. Adds
CLIENT_CLOSED_REQUEST/SERVICE_UNAVAILABLE to the v2 error codes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CiHhAk2R1NryaS3R8n2yFz

Author: TheodoreSpeaks

apps/sim/app/api/v2/lib/response.ts

@@ -22,7 +22,9 @@ export type V2ErrorCode =
   | 'USAGE_LIMIT_EXCEEDED'
   | 'LOCKED'
   | 'RATE_LIMITED'
+  | 'CLIENT_CLOSED_REQUEST'
   | 'INTERNAL_ERROR'
+  | 'SERVICE_UNAVAILABLE'
 
 const STATUS_BY_CODE: Record<V2ErrorCode, number> = {
   BAD_REQUEST: 400,
@@ -35,7 +37,9 @@ const STATUS_BY_CODE: Record<V2ErrorCode, number> = {
   UNSUPPORTED_MEDIA_TYPE: 415,
   LOCKED: 423,
   RATE_LIMITED: 429,
+  CLIENT_CLOSED_REQUEST: 499,
   INTERNAL_ERROR: 500,
+  SERVICE_UNAVAILABLE: 503,
 }
 
 /**