fix: detect platform on video create, remove hardcoded twitter default

backend/app/models.py

@@ -12,7 +12,7 @@ class Video(Base):
     task_id = Column(String(64), unique=True, index=True, nullable=False)
     url = Column(String(512), nullable=False, index=True)
     title = Column(String(512), default="")
-    platform = Column(String(32), default="twitter")
+    platform = Column(String(32), default="")
     thumbnail = Column(String(1024), default="")
     quality = Column(String(32), default="")
     format_id = Column(String(64), default="")

backend/app/routes/download.py

@@ -12,7 +12,7 @@ from app.schemas import DownloadRequest, DownloadResponse, TaskStatus
 from app.database import get_db, async_session
 from app.models import Video, DownloadLog
 from app.auth import get_current_user, optional_auth
-from app.services.downloader import download_video, get_video_path
+from app.services.downloader import download_video, get_video_path, detect_platform
 
 logger = logging.getLogger(__name__)
 router = APIRouter(prefix="/api", tags=["download"])
@@ -154,7 +154,8 @@ async def start_download(req: DownloadRequest, background_tasks: BackgroundTasks
         return DownloadResponse(task_id=existing.task_id, status="done")
 
     task_id = str(uuid.uuid4())[:8]
-    video = Video(task_id=task_id, url=req.url, quality=req.quality, format_id=req.format_id, status="pending")
+    video = Video(task_id=task_id, url=req.url, quality=req.quality, format_id=req.format_id,
+                  status="pending", platform=detect_platform(req.url))
     db.add(video)
     await db.commit()
     background_tasks.add_task(_do_download, task_id, req.url, req.format_id)

backend/app/services/downloader.py

@@ -55,6 +55,17 @@ def _is_pornhub_url(url: str) -> bool:
     return bool(PORNHUB_URL_RE.match(url))
 
 
+def detect_platform(url: str) -> str:
+    """Detect platform from URL."""
+    if _is_twitter_url(url):
+        return "twitter"
+    if _is_youtube_url(url):
+        return "youtube"
+    if _is_pornhub_url(url):
+        return "pornhub"
+    return "unknown"
+
+
 def _is_twitter_url(url: str) -> bool:
     return bool(TWITTER_URL_RE.match(url))
 
@@ -556,5 +567,5 @@ def download_video(url: str, format_id: str = "best", progress_callback=None) ->
         "filename": os.path.basename(filename),
         "file_path": filename,
         "file_size": file_size,
-        "platform": "twitter",
+        "platform": detect_platform(url),
     }