Initial commit: Maskarr - Tracker proxy for *arr apps

- HTTP proxy server to modify User-Agent and headers for private trackers
  - Web UI with collapsible tracker cards and real-time validation
  - Multi-tracker support with persistent JSON configuration
  - Thread-safe configuration management
  - Full HTTP methods support (GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS)
  - REST API for tracker management
  - Docker support with multi-architecture builds (amd64, arm64, arm/v7)
  - CI/CD workflows for GitHub Actions and Gitea Actions
  - Automatic publishing to GitHub Container Registry and Gitea Registry

maskarr_config.json

@@ -0,0 +1,5 @@
+{
+  "trackers": {},
+  "port": 8888,
+  "log_requests": true
+}