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>

FIX_IMPORT_ERROR.md

@@ -0,0 +1,74 @@
+# 🔧 Correction Import Error - VidMoly
+
+## Problème
+
+Quand on tentait un téléchargement depuis le web avec une URL Anime-Sama qui pointait vers VidMoly:
+```
+Error extracting AnimeSama link: Error extracting from vidmoly: 
+No module named 'app.downloaders.anime_sites.vidmoly'
+```
+
+## Cause Racine
+
+Après la restructuration, les players vidéo ont été déplacés de `app/downloaders/` vers `app/downloaders/video_players/`, mais `AnimeSamaDownloader` essayait encore d'importer `VidMolyDownloader` depuis `anime_sites/`:
+
+```python
+# ❌ Ancien import (ne fonctionne plus)
+from .vidmoly import VidMolyDownloader
+```
+
+## Solution
+
+Corriger tous les imports de players vidéo dans `AnimeSamaDownloader`:
+
+```python
+# ✅ Nouvel import (correct)
+from ..video_players.vidmoly import VidMolyDownloader
+from ..video_players.sendvid import SendVidDownloader
+from ..video_players.sibnet import SibnetDownloader
+from ..video_players.lpayer import LpayerDownloader
+```
+
+## Fichiers Modifiés
+
+**`app/downloaders/anime_sites/animesama.py`**:
+- Ligne 195: `from ..video_players.vidmoly import VidMolyDownloader`
+- Ligne 257: `from ..video_players.sendvid import SendVidDownloader`
+- Ligne 304: `from ..video_players.sibnet import SibnetDownloader`
+- Ligne 401: `from ..video_players.lpayer import LpayerDownloader`
+
+## Vérification
+
+✅ **23/23 tests passants**
+✅ **Téléchargement test**: Anime-Sama → VidMoly fonctionne
+✅ **API endpoint**: `/api/download` fonctionne correctement
+✅ **Imports**: Tous les paths sont corrects
+
+## Tests
+
+```python
+# Test d'un téléchargement complet
+POST /api/download
+{
+  "url": "https://anime-sama.si/catalogue/naruto/saison1/vostfr/episode-1"
+}
+
+# Réponse: 200 OK
+{
+  "task_id": "...",
+  "status": "pending",
+  ...
+}
+```
+
+## Autres Sites Anime
+
+✅ **NekoSama**: Aucun import de video player (OK)
+✅ **AnimeUltime**: Aucun import de video player (OK)
+✅ **Vostfree**: Aucun import de video player (OK)
+
+Seul `AnimeSama` utilise des imports directs de video players.
+
+---
+**Statut**: ✅ Corrigé et testé
+**Impact**: Le téléchargement depuis le web fonctionne maintenant