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/app/health_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 	"time"
 
@@ -12,6 +13,7 @@ import (
 
 	"galo/internal/config"
 	"galo/internal/storage"
+	"galo/internal/video"
 )
 
 func mustSigner(t *testing.T) *storage.Signer {
@@ -58,4 +60,23 @@ func TestHealthStorageLabel(t *testing.T) {
 	if body := call(); body["s3"] != "ok" {
 		t.Fatalf("expected default s3 label, got %v", body)
 	}
+
+	// A missing toolchain reports video unavailable without degrading the service.
+	if body := call(); body["video"] != "unavailable" {
+		t.Fatalf("expected video unavailable, got %v", body)
+	}
+	if body := call(); body["status"] != "ok" {
+		t.Fatalf("video unavailability must not degrade status, got %v", body)
+	}
+
+	// A resolvable toolchain reports video ok. The test binary is a known
+	// executable on every platform.
+	self, err := os.Executable()
+	if err != nil {
+		t.Fatalf("executable: %v", err)
+	}
+	srv.videoTools = video.Detect(config.Video{FFmpegPath: self, FFprobePath: self})
+	if body := call(); body["video"] != "ok" {
+		t.Fatalf("expected video ok, got %v", body)
+	}
 }