frontend: Migrate to jotai and urql

This cuts the bundle size by 50% and makes it easier to reason about state.
It removes the usage of react-router-dom and replaces it with a simple router atom based on jotai-location.
Since the screens will be quite simple, I don't expect that we'll need the advanced caching features of react-relay, hence the switch to urql.

frontend/codegen.ts

@@ -0,0 +1,16 @@
+import { CodegenConfig } from "@graphql-codegen/cli";
+
+const config: CodegenConfig = {
+  schema: "./schema.graphql",
+  documents: ["src/**/*.tsx", "!src/gql/**/*"],
+  ignoreNoDocuments: true, // for better experience with the watcher
+  generates: {
+    "./src/gql/": {
+      preset: "client",
+      plugins: [],
+    },
+  },
+  hooks: { afterAllFileWrite: ["eslint --fix"] },
+};
+
+export default config;