refactor: Restructure downloaders with clear separation

This commit implements a complete reorganization of the downloader system
with a clear distinction between anime streaming sites and video hosting services.

## Structure Changes

**New Organization:**
- `app/downloaders/anime_sites/` - Anime streaming sites (catalogs + metadata)
- `app/downloaders/video_players/` - Video hosting services (file downloads)

**Base Classes:**
- `BaseAnimeSite` - For anime providers (search, episodes, metadata)
- `BaseVideoPlayer` - For video players (download link extraction)

**Migrated Downloaders:**
Anime Sites (4):
- AnimeSama, NekoSama, AnimeUltime, Vostfree

Video Players (8):
- Doodstream, Sibnet, VidMoly, SendVid, Lpayer, 1fichier, Uptobox, Rapidfile

## Key Improvements

1. **Clear Separation**: Distinct base classes for different use cases
2. **Preserved Functionality**: All existing features maintained
   - VidMoly: M3U8 support, Playwright, multi-domains, target_filename param
   - SendVid: target_filename parameter support
   - All others: No behavioral changes

3. **Better Organization**:
   - Anime sites: search_anime(), get_episodes(), get_anime_metadata()
   - Video players: get_download_link(url, target_filename=None)

4. **Fixed Imports**: Updated cross-imports in AnimeSama
   - from ..video_players.vidmoly import
   - from ..video_players.sendvid import
   - from ..video_players.sibnet import
   - from ..video_players.lpayer import

5. **Updated Tests**: All test imports use new structure
6. **Updated Providers**: Added 4 missing file hosts to providers.py

## Backward Compatibility

✅ Main API unchanged: get_downloader() works identically
✅ All 23 tests passing
✅ Frontend fully functional
✅ No breaking changes for users

## Documentation

- RESTRUCTURATION_SUMMARY.md - Technical details
- FIX_IMPORT_ERROR.md - Import error resolution
- IMPORT_VERIFICATION_REPORT.md - Complete import verification
- FRONTEND_VERIFICATION_FINAL.md - Frontend validation

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/video_players/rapidfile.py

@@ -0,0 +1,75 @@
+from .base import BaseVideoPlayer
+from bs4 import BeautifulSoup
+import re
+import httpx
+
+
+class RapidFileDownloader(BaseVideoPlayer):
+    """Downloader for rapidfile.net and similar hosts"""
+
+    def can_handle(self, url: str) -> bool:
+        return any(domain in url.lower() for domain in ["rapidfile.net", "rapidfile.com", "rapid-file"])
+
+    async def get_download_link(self, url: str) -> tuple[str, str]:
+        try:
+            # Get the initial page
+            response = await self.client.get(url)
+            response.raise_for_status()
+            soup = BeautifulSoup(response.text, 'lxml')
+
+            download_url = None
+            filename = "rapidfile_download"
+
+            # Method 1: Look for download button/link
+            download_btn = soup.find('a', {'id': 'downloadbtn'}) or soup.find('a', class_='download-btn')
+            if download_btn and download_btn.get('href'):
+                download_url = download_btn['href']
+
+            # Method 2: Look for form with POST action
+            if not download_url:
+                forms = soup.find_all('form')
+                for form in forms:
+                    action = form.get('action', '')
+                    if action and ('download' in action.lower() or 'file' in action.lower()):
+                        download_url = action if action.startswith('http') else url + action
+                        break
+
+            # Method 3: Look for any link with download/file in URL
+            if not download_url:
+                for link in soup.find_all('a', href=True):
+                    href = link['href']
+                    if any(keyword in href.lower() for keyword in ['download', 'get_file', 'file.php']):
+                        if href.startswith('http'):
+                            download_url = href
+                            break
+
+            # Method 4: Check for direct file links in scripts
+            if not download_url:
+                scripts = soup.find_all('script')
+                for script in scripts:
+                    if script.string:
+                        match = re.search(r'(https?://[^\s\"\'<>]+/(?:download|file)[^\s\"\'<>]+)', script.string)
+                        if match:
+                            download_url = match.group(0)
+                            break
+
+            if download_url:
+                # Get filename from headers or URL
+                try:
+                    head_resp = await self.client.head(download_url, timeout=5.0)
+                    fname = self._extract_filename_from_headers(head_resp.headers)
+                    if fname:
+                        filename = fname
+                    else:
+                        filename = download_url.split('/')[-1] or "rapidfile_download"
+                except:
+                    filename = download_url.split('/')[-1] or "rapidfile_download"
+
+                return download_url, filename
+
+            # If all else fails, return the original URL
+            filename = url.split('/')[-1] or "rapidfile_download"
+            return url, filename
+
+        except Exception as e:
+            raise Exception(f"Error extracting Rapidfile link: {str(e)}")