feat: CI orchestrator — Lambda dispatch + Fargate routing + cancel

dispatch: receives Gitea webhook, routes by runs-on label to Fargate
  tasks (go/node/docker/godot) or Lambda executor (deploy).
  Path filter evaluation, DynamoDB run tracking, cancel via StopTask.
exec: lightweight Lambda for deploy-only jobs (S3 sync, ECS update).
SAM template: API Gateway + 2 Lambdas + DynamoDB + cleanup cron.

orchestrator/exec/go.mod

@@ -0,0 +1,8 @@
+module tinqs.com/tinqs/ci/orchestrator/exec
+
+go 1.23
+
+require (
+	github.com/aws/aws-lambda-go v1.47.0
+	gopkg.in/yaml.v3 v3.0.1
+)