feat: migrate to Poetry and implement multi-backend DNS management ✨

- Migrated from setuptools to Poetry; added pyproject.toml, poetry.lock,
  poetry.toml and .python-version (Python 3.11.12)
- Built out full directdnsonly Python package with BIND and CoreDNS MySQL
  backends, CherryPy REST API, persist-queue worker, and vyper-based config
- Auth credentials now read from config/env (app.auth_username/password)
  rather than hardcoded; override via DADNS_APP_AUTH_PASSWORD env var
- Added Dockerfile.deepseek: Python 3.11 slim + BIND9 + Poetry install
- Rewrote docker-compose.yml for local dev stack (MySQL + dadns services)
- Added SQL schema, docker/ BIND configs, justfile, tests, and README
- Expanded .gitignore for Poetry/Python project artifacts

directdnsonly/app/api/health.py

@@ -0,0 +1,24 @@
+import cherrypy
+from loguru import logger
+
+
+class HealthAPI:
+    def __init__(self, backend_registry):
+        self.registry = backend_registry
+
+    @cherrypy.expose
+    def health(self):
+        status = {"status": "OK", "backends": []}
+
+        for name, backend in self.registry.get_available_backends().items():
+            status["backends"].append(
+                {
+                    "name": name,
+                    "status": (
+                        "active" if backend().zone_exists("test") else "unavailable"
+                    ),
+                }
+            )
+
+        logger.debug("Health check performed")
+        return status