feat: Complete Sonarr integration with security enhancements

This commit adds comprehensive Sonarr webhook integration and implements
critical security improvements identified in code review.

## Sonarr Integration
- Full webhook support for Grab, Download, Rename, Delete, and Test events
- HMAC SHA256 signature verification for webhook authentication
- Series mapping system (Sonarr TVDB ID → Anime Provider URL)
- 11 new API endpoints for configuration, mappings, search, and downloads
- Comprehensive test suite (31 tests, all passing)
- Complete documentation in docs/SONARR_INTEGRATION.md

## Security Enhancements
- CORS restricted to specific origins (user's IP: 192.168.1.204:3000)
- Path traversal prevention via sanitize_filename() and is_safe_filename()
- Structured logging infrastructure (replaced all print() statements)
- Environment-based configuration with .env support
- Filename sanitization prevents malicious path attacks

## New Features
- Lpayer and Sibnet downloader support
- Kitsu API integration for anime metadata
- Recommendation engine based on download history
- Latest releases endpoint for new anime
- Modular web interface with component-based templates

## Configuration
- Centralized settings via app/config.py with pydantic-settings
- Sonarr config auto-created in config/ directory
- Example configurations provided for easy setup

## Tests
- 31 Sonarr integration tests (23 functionality + 9 security)
- 100+ tests passing in core test files
- Security utilities fully tested

## Documentation
- Updated CLAUDE.md with Sonarr and testing info
- Added IMPROVEMENTS_2024-01-24.md analysis
- Added SONARR_IMPLEMENTATION.md technical summary

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>

templates/components/search_tab.html

@@ -0,0 +1,24 @@
+<!-- Search Tab -->
+<div id="tab-search" class="tab-content">
+    <div class="url-form">
+        <div class="input-group">
+            <input
+                type="text"
+                id="searchInput"
+                placeholder="Rechercher un anime (ex: Frieren, One Piece...)"
+            >
+            <button type="button" class="btn-primary" onclick="handleSearch()">
+                <svg fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M21 21l-6-6m2-5a7 7 0 11-14 0 7 7 0 0114 0z"></path>
+                </svg>
+                Rechercher
+            </button>
+        </div>
+        <div style="margin-top: 10px; padding: 10px; background: rgba(0, 217, 255, 0.1); border-radius: 8px; font-size: 12px; color: #aaa;">
+            💡 <strong>Info:</strong> La recherche utilise MyAnimeList pour afficher la fiche complète de l'anime (synopsis, saisons, etc.) et trouve les sources de streaming disponibles.
+        </div>
+    </div>
+
+    <!-- Anime details and streaming results -->
+    <div id="animeSearchResults"></div>
+</div>