feat: Add SendVid downloader support

Add complete support for SendVid video hosting service used by Anime-Sama
for anime series like Hell's Paradise.

Changes:
- Create SendVidDownloader class with proper headers to avoid 403 errors
- Add SendVid detection and handling in AnimeSamaDownloader
- Update download_manager to include SendVid-specific headers
- Support custom episode naming (e.g., "Hells Paradise - Episode 01.mp4")

Technical details:
- SendVid embed pages require User-Agent and Referer headers
- Direct MP4 URLs extracted from <source> tags with IP/time-based parameters
- Tested with Hell's Paradise Episode 01 (7MB, 24min, 1280x720)

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

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

app/downloaders/uptobox.py

@@ -0,0 +1,59 @@
+from .base import BaseDownloader
+from bs4 import BeautifulSoup
+import re
+
+
+class UptoboxDownloader(BaseDownloader):
+    """Downloader for uptobox.com"""
+
+    BASE_DOMAINS = ["uptobox.com", "uptobox.fr"]
+
+    def can_handle(self, url: str) -> bool:
+        return any(domain in url.lower() for domain in self.BASE_DOMAINS)
+
+    async def get_download_link(self, url: str) -> tuple[str, str]:
+        """Extract direct download link from uptobox"""
+        try:
+            response = await self.client.get(url, follow_redirects=True)
+            soup = BeautifulSoup(response.text, 'lxml')
+
+            # Method 1: Look for direct download button/link
+            download_btn = soup.find('a', {'id': 'directDownload'}) or soup.find('a', class_='download-btn')
+            if download_btn and download_btn.get('href'):
+                href = download_btn['href']
+                filename = self._extract_filename_from_url(url) or "uptobox_file"
+                return href, filename
+
+            # Method 2: Look for any download link in page
+            links = soup.find_all('a', href=True)
+            for link in links:
+                href = link['href']
+                text = link.get_text().lower()
+                if any(keyword in text for keyword in ['download', 'télécharger', 'ddl']):
+                    if href.startswith('http'):
+                        filename = self._extract_filename_from_url(url) or "uptobox_file"
+                        return href, filename
+
+            # Method 3: Return the original URL (uptobox handles downloads directly)
+            filename = self._extract_filename_from_url(url) or "uptobox_file"
+            return url, filename
+
+        except Exception as e:
+            raise Exception(f"Error extracting Uptobox link: {str(e)}")
+
+    def _extract_filename_from_url(self, url: str) -> str | None:
+        """Try to extract filename from URL"""
+        # Look for filename parameter in URL
+        match = re.search(r'[&?]filename=([^&]+)', url)
+        if match:
+            from urllib.parse import unquote
+            return unquote(match.group(1))
+
+        # Extract from path
+        parts = url.split('/')
+        if len(parts) > 0:
+            last_part = parts[-1]
+            if '.' in last_part:
+                return last_part
+
+        return None