Add Debian packaging support with configurable binding

- Add complete debian/ packaging structure for .deb creation
- Support BIND_ADDR environment variable (defaults to 0.0.0.0)
- Create /etc/default/naas config file (defaults to localhost binding)
- Systemd service reads from /etc/default/naas
- Package installs but does not auto-enable service
- Upgrades restart service only if already enabled
- Proper user creation and cleanup on install/remove

Key files:
- debian/control: Package metadata with rustup build dependency support
- debian/naas.default: Configuration template for /etc/default/naas
- debian/naas.service: Updated systemd service with EnvironmentFile
- debian/postinst: Creates naas user, restarts on upgrade if enabled
- debian/prerm: Stops service on removal
- debian/postrm: Cleans up user on purge
- src/main.rs: Added BIND_ADDR support for configurable binding

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

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

debian/changelog

@@ -0,0 +1,10 @@
+naas (1.0.0-1) unstable; urgency=medium
+
+  * Initial release of NaaS (No as a Service)
+  * HTTP service that always responds with "no"
+  * Multiple response formats: text, JSON, XML, YAML, boolean
+  * Minimalist web frontend and interactive playground
+  * Health check endpoint
+  * Systemd service integration
+
+ -- Ole-Morten Duesund <olemd@glemt.net>  Fri, 27 Sep 2024 15:00:00 +0200