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/db/migrate_sqlite_test.go

@@ -1,8 +1,10 @@
 package db
 
 import (
+	"database/sql"
 	"io/fs"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	assets "galo"
@@ -34,4 +36,38 @@ func TestMigrateSQLite(t *testing.T) {
 	if n != 1 {
 		t.Fatalf("objects table missing after migration")
 	}
+
+	assertColumn(t, db, "photos", "kind")
+	assertColumn(t, db, "photos", "duration_ms")
+	assertColumn(t, db, "variant_jobs", "kind")
+
+	var ddl string
+	if err := db.QueryRow(`SELECT sql FROM sqlite_master WHERE type='table' AND name='photo_objects'`).Scan(&ddl); err != nil {
+		t.Fatalf("photo_objects ddl: %v", err)
+	}
+	if !strings.Contains(ddl, "playback") {
+		t.Fatalf("photo_objects role constraint missing playback: %s", ddl)
+	}
+}
+
+func assertColumn(t *testing.T, db *sql.DB, table, column string) {
+	t.Helper()
+	rows, err := db.Query(`PRAGMA table_info(` + table + `)`)
+	if err != nil {
+		t.Fatalf("table_info %s: %v", table, err)
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var cid int
+		var name, typ string
+		var notNull, pk int
+		var dflt any
+		if err := rows.Scan(&cid, &name, &typ, &notNull, &dflt, &pk); err != nil {
+			t.Fatalf("scan table_info %s: %v", table, err)
+		}
+		if name == column {
+			return
+		}
+	}
+	t.Fatalf("column %s.%s missing", table, column)
 }