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

templates/components/login_prompt.html

@@ -0,0 +1,4 @@
+<div class="login-prompt" style="text-align: center; padding: 40px 20px;">
+    <i class="fas fa-lock" style="font-size: 2rem; color: #00d9ff; margin-bottom: 15px;"></i>
+    <p style="color: #888; font-size: 0.95rem;">Connectez-vous pour accéder à cette section.</p>
+</div>