Vendor backend and frontend into the monorepo

The submodule collapse was only half applied: .gitmodules was deleted but
backend/ and frontend/ were still recorded as gitlinks, so none of their
files were tracked. Replace the gitlinks with the real trees.

Also untrack .env (it carried placeholder secrets) in favour of a tracked
.env.example, drop the committed __pycache__, and narrow the blanket *.png
ignore that would have swallowed design assets.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/utils.ts

@@ -0,0 +1,31 @@
+import { AxiosError } from "axios"
+import type { ApiError } from "./client"
+
+function extractErrorMessage(err: ApiError): string {
+  if (err instanceof AxiosError) {
+    return err.message
+  }
+
+  const errDetail = (err.body as any)?.detail
+  if (Array.isArray(errDetail) && errDetail.length > 0) {
+    return errDetail[0].msg
+  }
+  return errDetail || "Something went wrong."
+}
+
+export const handleError = function (
+  this: (msg: string) => void,
+  err: ApiError,
+) {
+  const errorMessage = extractErrorMessage(err)
+  this(errorMessage)
+}
+
+export const getInitials = (name: string): string => {
+  return name
+    .split(" ")
+    .slice(0, 2)
+    .map((word) => word[0])
+    .join("")
+    .toUpperCase()
+}