feat: Add series TV support with Vidzy HLS downloads and duplicate prevention

Major improvements:
- Series TV support via FS7 provider with dedicated search endpoint
- Vidzy downloader now uses Playwright for JS obfuscation and ffmpeg for HLS streams
- Episode filenames properly named (Series Title - Episode X) instead of master.m3u8.mp4
- Duplicate download prevention: checks existing tasks before creating new ones
- Removed host preference system in favor of intelligent URL-based detection

Technical changes:
- Vidzy: Added Playwright extraction and M3U8→MP4 conversion with ffmpeg
- FS7: Episodes now use pipe format (video_url|series_url|episode_title)
- DownloadManager: Extract target_filename from pipe URL and prevent duplicates
- UI: New Series tab with search, recommendations, and releases sections
- Anime-Sama: Removed hardcoded host preferences, uses site's URL order

Generated with [Claude Code](https://claude.com/claude-code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

app/download_manager.py

@@ -30,6 +30,25 @@ class DownloadManager:
         return list(self.tasks.values())
 
     def create_task(self, request: DownloadRequest) -> DownloadTask:
+        # Check for existing tasks with the same URL
+        # Extract actual URL from pipe-separated format
+        url_to_check = request.url.split('|')[0] if '|' in request.url else request.url
+
+        # Look for existing non-failed tasks with the same URL
+        for existing_task in self.tasks.values():
+            existing_url = existing_task.url.split('|')[0] if '|' in existing_task.url else existing_task.url
+
+            # If same URL and task is not failed/cancelled/completed
+            if existing_url == url_to_check and existing_task.status not in [
+                DownloadStatus.FAILED,
+                DownloadStatus.CANCELLED,
+                DownloadStatus.COMPLETED
+            ]:
+                logger.info(f"Duplicate download detected: {url_to_check[:80]}...")
+                logger.info(f"Returning existing task: {existing_task.id}")
+                return existing_task
+
+        # No duplicate found, create new task
         task_id = str(uuid.uuid4())
         task = DownloadTask(
             id=task_id,
@@ -103,7 +122,17 @@ class DownloadManager:
 
                 # Get downloader and extract link
                 downloader = get_downloader(task.url)
-                download_url, filename = await downloader.get_download_link(task.url)
+
+                # Extract episode title from pipe-separated URL if present
+                # Format: video_url|anime_page_url|episode_title
+                target_filename = None
+                if '|' in task.url:
+                    parts = task.url.split('|')
+                    if len(parts) >= 3:
+                        target_filename = parts[2].strip()
+                        logger.debug(f"Extracted target filename from pipe: {target_filename}")
+
+                download_url, filename = await downloader.get_download_link(task.url, target_filename)
 
                 logger.info(f"Download URL: {download_url[:100] if len(download_url) > 100 else download_url}")
                 logger.debug(f"Downloader filename: {filename}")