fix(drafts): swap crypto.randomUUID() for the project's randomUUID helper

crypto.randomUUID() is gated on a secure origin (HTTPS or localhost).
Self-hosted Windmill instances often run on a bare HTTP origin or a
LAN IP where the WebCrypto API is unavailable, so the /add redirect
would throw before issuing the 307. Use the existing RFC4122 v4 helper
in FlowChatManager that the rest of the codebase already imports for
this exact reason.

frontend/src/lib/draftAddRedirect.ts

@@ -1,6 +1,7 @@
 import { redirect } from '@sveltejs/kit'
 import { base } from '$app/paths'
 import { getUsernameForNamespace } from '$lib/userNamespace'
+import { randomUUID } from '$lib/components/flows/conversations/FlowChatManager.svelte'
 
 /**
  * Shared `load` for every `/{scripts,flows,apps,apps_raw}/add` route.
@@ -14,11 +15,16 @@ import { getUsernameForNamespace } from '$lib/userNamespace'
  * `{base}/{editPrefix}/<that-path>?new_draft=true&<existing-params>`.
  * The `new_draft=true` flag tells the edit route to seed an empty
  * editor instead of 404-ing on the autogenerated path.
+ *
+ * Uses the project's `randomUUID` helper rather than
+ * `crypto.randomUUID()` — the WebCrypto version is unavailable on
+ * non-secure origins (HTTP, local IPs over LAN), and self-hosted
+ * Windmill instances frequently run that way.
  */
 export function makeDraftAddLoad(editPrefix: string) {
 	return ({ url }: { url: URL }) => {
 		const username = getUsernameForNamespace()
-		const uuid = crypto.randomUUID()
+		const uuid = randomUUID()
 		const params = new URLSearchParams(url.searchParams)
 		params.set('new_draft', 'true')
 		redirect(307, `${base}/${editPrefix}/u/${username}/draft_${uuid}?${params.toString()}`)