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/providers.py

@@ -46,7 +46,7 @@ FILE_HOSTS = {
     },
     "doodstream": {
         "name": "Doodstream",
-        "domains": ["doodstream.com", "dood.to", "dood.lol", "dood.cx", "dood.so", "dood.watch"],
+        "domains": ["doodstream.com", "dood.stream", "dood.to", "dood.lol", "dood.cx", "dood.so", "dood.watch", "dood.sh"],
         "icon": "🎥",
         "color": "#f7b731"
     },
@@ -55,6 +55,30 @@ FILE_HOSTS = {
         "domains": ["rapidfile.net", "rapidfile.com"],
         "icon": "⚡",
         "color": "#ff6b6b"
+    },
+    "vidmoly": {
+        "name": "VidMoly",
+        "domains": ["vidmoly.to", "vidmoly.org", "vidmoly.biz"],
+        "icon": "🎬",
+        "color": "#a29bfe"
+    },
+    "sendvid": {
+        "name": "SendVid",
+        "domains": ["sendvid.com", "sendvid.io"],
+        "icon": "📤",
+        "color": "#fd79a8"
+    },
+    "sibnet": {
+        "name": "Sibnet",
+        "domains": ["sibnet.ru", "video.sibnet.ru"],
+        "icon": "🎞️",
+        "color": "#00cec9"
+    },
+    "lpayer": {
+        "name": "Lplayer",
+        "domains": ["lpayer.embed4me.com", "lpayer.com", "lplayer.fr"],
+        "icon": "▶️",
+        "color": "#e17055"
     }
 }