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/unfichier.py

@@ -0,0 +1,51 @@
+from .base import BaseDownloader
+from bs4 import BeautifulSoup
+import re
+import httpx
+
+
+class UnFichierDownloader(BaseDownloader):
+    """Downloader for 1fichier.com"""
+
+    def can_handle(self, url: str) -> bool:
+        return any(domain in url.lower() for domain in ["1fichier.com", "1fichier.fr"])
+
+    async def get_download_link(self, url: str) -> tuple[str, str]:
+        try:
+            # Initial page
+            response = await self.client.get(url)
+            response.raise_for_status()
+
+            # Check if we need to wait (download button)
+            soup = BeautifulSoup(response.text, 'lxml')
+
+            # Check for direct download link
+            download_link = soup.find('a', class_='btn btn-download')
+            if download_link and download_link.get('href'):
+                download_url = download_link['href']
+                # Follow to get headers for filename
+                head_resp = await self.client.head(download_url)
+                filename = self._extract_filename_from_headers(head_resp.headers)
+                if not filename:
+                    filename = download_url.split('/')[-1] or "downloaded_file"
+                return download_url, filename
+
+            # Alternative: look for any download link in the page
+            for link in soup.find_all('a', href=True):
+                href = link['href']
+                if href.startswith('http') and '1fichier' not in href:
+                    # Try to head the URL to see if it's a file
+                    try:
+                        head_resp = await self.client.head(href, timeout=5.0)
+                        if 'content-length' in head_resp.headers or 'attachment' in head_resp.headers.get('content-disposition', ''):
+                            filename = self._extract_filename_from_headers(head_resp.headers)
+                            if not filename:
+                                filename = href.split('/')[-1] or "downloaded_file"
+                            return href, filename
+                    except:
+                        continue
+
+            raise Exception("Could not find download link on page")
+
+        except Exception as e:
+            raise Exception(f"Error extracting 1fichier link: {str(e)}")