Refactor UI assets and harden quality checks

tests/test_dependencies.py

@@ -0,0 +1,14 @@
+import base64
+
+from karldns.dependencies import _basic_auth_password
+
+
+def _basic_header(username: str, password: str) -> str:
+    token = base64.b64encode(f"{username}:{password}".encode()).decode()
+    return f"Basic {token}"
+
+
+def test_basic_auth_password_extracts_only_basic_passwords() -> None:
+    assert _basic_auth_password(_basic_header("admin", "secret")) == "secret"
+    assert _basic_auth_password("Bearer token") is None
+    assert _basic_auth_password(None) is None