feat: fix auth, provider health checks, search, and redesign UI

- Fix register/login: dict-style access on UserTable ORM objects
- Fix HTMX auth: inject JWT token in all HTMX request headers
- Fix FS7 search: use DLE AJAX endpoint /engine/ajax/search.php
- Fix ZT search: use ?p=series&search=QUERY (not DLE format)
- Fix provider health: load hardcoded providers + domain manager
- Add self.id to all anime/series providers
- Redesign homepage: Netflix-style horizontal scroll cards (.hc)
- Redesign search results: grouped by title, poster + synopsis + 3 buttons
- Add Télécharger dropdown: season download + episode picker
- Fix navbar CSS: restore .tabs flex layout, remove orphan rules
- Fix HTMX spinner: remove inline display:none, use CSS indicator
- Add AGENTS.md files across project for developer documentation

app/downloaders/AGENTS.md

@@ -0,0 +1,49 @@
+# Downloaders (app/downloaders/)
+
+## OVERVIEW
+3-tier scraper architecture: anime catalogs → series catalogs → video players. Factory pattern routes URLs through each tier.
+
+## STRUCTURE
+```
+downloaders/
+├── __init__.py          # get_downloader(url) — 3-tier factory + GenericDownloader
+├── base.py              # Legacy BaseDownloader (kept for compat)
+├── anime_sites/         # Anime streaming catalogs (see anime_sites/AGENTS.md)
+│   ├── __init__.py      # get_anime_site(url) factory
+│   ├── base.py          # BaseAnimeSite abstract class
+│   └── *.py             # 5 anime providers
+├── series_sites/        # TV series catalogs (see series_sites/AGENTS.md)
+│   ├── __init__.py      # get_series_site(url) factory
+│   ├── base.py          # BaseSeriesSite abstract class
+│   └── fs7.py           # 1 series provider
+└── video_players/       # File hosting extractors (see video_players/AGENTS.md)
+    ├── __init__.py      # get_video_player(url) factory
+    ├── base.py          # BaseVideoPlayer abstract class
+    └── *.py             # 13 video player handlers
+```
+
+## WHERE TO LOOK
+
+| Need | File | Notes |
+|------|------|-------|
+| Route URL to downloader | `__init__.py:32` | `get_downloader(url)` tries anime→series→video→generic |
+| Add anime provider | `anime_sites/` | Inherit BaseAnimeSite, register in anime_sites/__init__.py |
+| Add series provider | `series_sites/` | Inherit BaseSeriesSite, register in series_sites/__init__.py |
+| Add video player | `video_players/` | Inherit BaseVideoPlayer, register in video_players/__init__.py |
+| Provider domains/icons | `app/providers.py` | Separate from downloader code |
+
+## CONVENTIONS
+
+**URL pipe format**: `video_url|anime_page_url|episode_title` — metadata preserved through tiers. Anime/series sites return player URLs (not direct downloads). Video players extract final download links.
+
+**Factory chain**: `get_downloader()` → `get_anime_site()` → `get_series_site()` → `get_video_player()` → `GenericDownloader`.
+
+**New provider checklist**: 1) Create .py inheriting base class, 2) Implement required methods, 3) Add to `__init__.py` factory list, 4) Add to `app/providers.py`.
+
+## ANTI-PATTERNS
+
+- Do NOT return None from `get_download_link()` — raise Exception
+- Do NOT use sync `requests` — always `httpx.AsyncClient`
+- Do NOT forget `await self.close()` — causes resource leaks
+- Do NOT skip `sanitize_filename()` on extracted filenames
+- Do NOT hardcode User-Agent per player — use base class headers