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>

.env.example

@@ -1,13 +1,31 @@
-# Ohm Streaming API Configuration
+# Ohm Stream Downloader Environment Configuration
 
-# Server
+# Application
+APP_NAME=Ohm Stream Downloader
+APP_VERSION=2.2
+DEBUG=false
+
+# Server Configuration
 HOST=0.0.0.0
-PORT=8000
+PORT=3000
 RELOAD=true
 
-# Paths
-UPLOAD_DIR=uploads
-STREAM_DIR=streams
+# Download Settings
+DOWNLOAD_DIR=downloads
+MAX_PARALLEL_DOWNLOADS=3
+CHUNK_SIZE=1048576
 
-# CORS
-ALLOWED_ORIGINS=*
+# CORS Origins (comma-separated)
+CORS_ORIGINS=http://localhost:3000,http://127.0.0.1:3000,http://192.168.1.204:3000
+
+# Storage Paths
+FAVORITES_STORAGE_PATH=favorites.json
+SONARR_CONFIG_PATH=config/sonarr.json
+SONARR_MAPPINGS_PATH=config/sonarr_mappings.json
+
+# API Timeouts
+HTTP_TIMEOUT=10.0
+DOWNLOAD_TIMEOUT=300
+
+# Logging
+LOG_LEVEL=INFO