Add MIT license and fix Debian packaging

- Add MIT License for maximum permissivity
- Update Cargo.toml with complete package metadata including license
- Update README.md with license information and explanation
- Fix Debian package systemd service installation conflict
  (remove manual installation, let debhelper handle it automatically)

The MIT License allows anyone to use, modify, and distribute this
software with minimal restrictions.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Cargo.toml

@@ -2,6 +2,14 @@
 name = "naas"
 version = "1.0.0"
 edition = "2021"
+license = "MIT"
+description = "No as a Service - A lightweight HTTP service that always says 'no'"
+repository = "https://kode.naiv.no/olemd/naas"
+homepage = "https://kode.naiv.no/olemd/naas"
+authors = ["Ole-Morten Duesund <olemd@glemt.net>"]
+keywords = ["http", "service", "api", "no", "rust"]
+categories = ["web-programming::http-server"]
+readme = "README.md"
 
 [dependencies]