Add frontend build to Python packaging. Remove dead code, cleanup.

scripts/build-frontend.py

@@ -0,0 +1,12 @@
+# noqa: INP001
+import subprocess
+
+from hatchling.builders.hooks.plugin.interface import BuildHookInterface
+
+
+class CustomBuildHook(BuildHookInterface):
+    def initialize(self, version, build_data):
+        super().initialize(version, build_data)
+        print("Building Cista frontend...")
+        subprocess.run("npm install --prefix frontend".split(" "), check=True)  # noqa: S603
+        subprocess.run("npm run build --prefix frontend".split(" "), check=True)  # noqa: S603