feat(models): expand Application with extended configuration

[andrasbacsai]

Summary

• Add ApplicationSettings struct for managing application feature flags (auto-deploy, HTTPS enforcement, preview deployments, git submodules, git LFS)
• Expand Application struct with ~50 new fields across multiple categories:
  • Git extended info (commit SHA, full URL)
  • Build configuration (install/build/start commands, base/publish directories, static image)
  • Docker configuration (Dockerfile, Docker Compose, registry images, custom options, labels, nginx config)
  • Networking (port mappings, domains, redirects, preview URL templates)
  • Health checks (path, port, host, method, scheme, return code, response text, interval, timeout, retries, start period)
  • Resource limits (CPU, memory, memory swap, memory reservation, memory swappiness, CPU shares, CPU set)
  • Deployment hooks (pre/post deployment commands and container references)
  • Webhook secrets for GitHub, GitLab, Bitbucket, Gitea (marked sensitive)
  • Miscellaneous (watch paths, swarm replicas, config hash)
• Organize fields with inline comments by functional category for better readability
• Hide internal fields (ID, EnvironmentID, DestinationID, SourceID, PrivateKeyID) from JSON and table output
• Add comprehensive test coverage:
  • Marshal/unmarshal roundtrip testing
  • Fixture-based testing with realistic application data
  • JSON serialization validation ensuring hidden fields are excluded
  • Update service tests with expanded field coverage
• Add test fixture (test/fixtures/application.json) with complete application configuration example