feat(phase-1.2): temporal SDK client, worker mgmt, k8s deployments

- internal/temporal/client.go: robust client with retry + TLS + health check
- internal/temporal/worker.go: worker creation, registration, lifecycle
- internal/temporal/context.go: timeout helpers
- k8s/worker-deployment.yaml: 2-10 replica HPA, health probes, security context
- k8s/workflow-runner-deployment.yaml: singleton runner with probes
- k8s/kustomization.yaml: updated resource list, removed missing ref

Tests: 11 pass (client_test.go + worker_test.go)
Build: go build ./... clean
Kustomize: dry-run validated

internal/temporal/context.go

@@ -0,0 +1,16 @@
+package temporal
+
+import (
+	"context"
+	"time"
+)
+
+// ContextWithTimeout creates a context with the given timeout.
+func ContextWithTimeout(timeout time.Duration) (context.Context, context.CancelFunc) {
+	return context.WithTimeout(context.Background(), timeout)
+}
+
+// ContextWithDefault creates a context with a default timeout of 10 seconds.
+func ContextWithDefault() (context.Context, context.CancelFunc) {
+	return context.WithTimeout(context.Background(), 10*time.Second)
+}