feat(deploy): per-service deploy queue, cancellable deployments, no-cache builds

- internal/deployqueue: serialized FIFO per service — concurrent deploys
  of one service no longer race (the container-name-conflict failure
  mode); different services still run in parallel.
- Deploys and rollbacks enqueue through the queue; a busy service
  returns status 'queued' and promotes when the active job finishes.
- POST /deployments/:id/cancel — queued jobs drop immediately
  (200 cancelled); active jobs get ctx cancelled so build/reconcile
  abort (202 cancelling, settles 'cancelled'); finished deployments
  return 409 NOT_CANCELLABLE.
- Redeploy and variables save now route through the same queue so they
  can't overlap a build; PUT /services/:id/variables accepts
  redeploy:true to apply env changes to running containers.
- no_cache on deployment create plumbs BuildRequest -> BuildOptions for
  nixpacks, dockerfile and railpack builders.
- CLI: deployments cancel, deploy --no-cache, variables set/unset
  --redeploy. MCP: containr_deployments_cancel; deploy/variables_set
  document no_cache/redeploy. UI: Cancel button + queued/cancelled
  badges on the deployments table. OpenAPI + types regenerated.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/deployqueue/queue_test.go

@@ -0,0 +1,142 @@
+package deployqueue
+
+import (
+	"context"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+func TestSerializesPerService(t *testing.T) {
+	q := New()
+	svc := uuid.New()
+
+	var active, maxActive int32
+	finish := make(chan struct{})
+	for i := 0; i < 3; i++ {
+		q.Enqueue(svc, Job{Run: func(ctx context.Context) {
+			if n := atomic.AddInt32(&active, 1); n > atomic.LoadInt32(&maxActive) {
+				atomic.StoreInt32(&maxActive, n)
+			}
+			<-finish // hold until released
+			atomic.AddInt32(&active, -1)
+		}})
+	}
+
+	deadline := time.After(2 * time.Second)
+	for atomic.LoadInt32(&active) < 1 {
+		select {
+		case <-deadline:
+			t.Fatal("first job never started")
+		default:
+			time.Sleep(time.Millisecond)
+		}
+	}
+	close(finish)
+	deadline = time.After(2 * time.Second)
+	for atomic.LoadInt32(&active) > 0 {
+		select {
+		case <-deadline:
+			t.Fatal("jobs did not drain")
+		default:
+			time.Sleep(time.Millisecond)
+		}
+	}
+	if got := atomic.LoadInt32(&maxActive); got != 1 {
+		t.Fatalf("expected max concurrency 1, got %d", got)
+	}
+}
+
+func TestDifferentServicesRunInParallel(t *testing.T) {
+	q := New()
+	started := make(chan struct{}, 2)
+	release := make(chan struct{})
+	for i := 0; i < 2; i++ {
+		q.Enqueue(uuid.New(), Job{Run: func(ctx context.Context) {
+			started <- struct{}{}
+			<-release
+		}})
+	}
+	for i := 0; i < 2; i++ {
+		select {
+		case <-started:
+		case <-time.After(2 * time.Second):
+			t.Fatal("parallel services did not both start")
+		}
+	}
+	close(release)
+}
+
+func TestCancelQueuedRemovesJob(t *testing.T) {
+	q := New()
+	svc := uuid.New()
+	release := make(chan struct{})
+	q.Enqueue(svc, Job{DeploymentID: uuid.New(), Run: func(ctx context.Context) { <-release }})
+
+	queuedID := uuid.New()
+	ran := make(chan struct{})
+	q.Enqueue(svc, Job{DeploymentID: queuedID, Run: func(ctx context.Context) { close(ran) }})
+
+	if got := q.Cancel(svc, queuedID); got != WasQueued {
+		t.Fatalf("expected WasQueued, got %v", got)
+	}
+	close(release)
+	select {
+	case <-ran:
+		t.Fatal("cancelled queued job still ran")
+	case <-time.After(200 * time.Millisecond):
+	}
+}
+
+func TestCancelActiveCancelsContext(t *testing.T) {
+	q := New()
+	svc := uuid.New()
+	id := uuid.New()
+	ctxDone := make(chan struct{})
+	q.Enqueue(svc, Job{DeploymentID: id, Run: func(ctx context.Context) {
+		<-ctx.Done()
+		close(ctxDone)
+	}})
+
+	deadline := time.After(2 * time.Second)
+	for {
+		q.mu.Lock()
+		_, ok := q.cancels[id]
+		q.mu.Unlock()
+		if ok {
+			break
+		}
+		select {
+		case <-deadline:
+			t.Fatal("job never registered")
+		default:
+			time.Sleep(time.Millisecond)
+		}
+	}
+	if got := q.Cancel(svc, id); got != WasActive {
+		t.Fatalf("expected WasActive, got %v", got)
+	}
+	select {
+	case <-ctxDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("active job context not cancelled")
+	}
+}
+
+func TestEnqueuePosition(t *testing.T) {
+	q := New()
+	svc := uuid.New()
+	release := make(chan struct{})
+	if pos := q.Enqueue(svc, Job{Run: func(ctx context.Context) { <-release }}); pos != 0 {
+		t.Fatalf("first job position = %d, want 0", pos)
+	}
+	if pos := q.Enqueue(svc, Job{Run: func(ctx context.Context) {}}); pos != 1 {
+		t.Fatalf("second job position = %d, want 1", pos)
+	}
+	if pos := q.Enqueue(svc, Job{Run: func(ctx context.Context) {}}); pos != 2 {
+		t.Fatalf("third job position = %d, want 2", pos)
+	}
+	close(release)
+}