feat(video): add video upload with remux/transcode playback

Add video as a media kind in photos: streaming upload with per-kind
limits, ffprobe metadata, poster frame reusing the image variant
pipeline, and a playback object (remux when web-compatible, else
h264/yuv420p/aac transcode). Video jobs run on a separate pool with a
long lease. Frontend gains a video viewer, grid badge/duration and
video upload.

backend/internal/photos/worker_test.go

@@ -7,7 +7,9 @@ import (
 
 	"github.com/jackc/pgx/v5/pgxpool"
 
+	"galo/internal/config"
 	"galo/internal/storage"
+	"galo/internal/video"
 )
 
 func TestWorkerGeneratesVariantsAndCollects(t *testing.T) {
@@ -140,6 +142,28 @@ func TestWorkerConcurrencySequentialAtOne(t *testing.T) {
 	}
 }
 
+func TestProcessVideoJobsSkipsWithoutTools(t *testing.T) {
+	// With no toolchain the video pass must return before touching the store,
+	// so a nil service is safe here.
+	w := NewWorker(&Service{}, time.Second, 10, time.Minute, 2)
+	w.processVideoJobs(context.Background())
+}
+
+func TestSetVideoConfiguresPool(t *testing.T) {
+	tools := video.Detect(config.Video{FFmpegPath: "definitely-missing-xyz", FFprobePath: "definitely-missing-xyz"})
+	w := &Worker{}
+	w.SetVideo(tools, 2)
+	if w.videoConc != 2 {
+		t.Fatalf("video concurrency = %d, want 2", w.videoConc)
+	}
+	if w.videoLease != videoJobLease {
+		t.Fatalf("video lease = %v, want %v", w.videoLease, videoJobLease)
+	}
+	if tools.Available() {
+		t.Fatal("missing toolchain should be unavailable")
+	}
+}
+
 func countObjects(t *testing.T, ctx context.Context, pool *pgxpool.Pool, ids []string) int {
 	t.Helper()
 	var n int