fix(api): set JSON Content-Type on onboarding-seed

POST /workspaces/onboarding-seed now sends application/json so servers that require it parse the body correctly.

Made-with: Cursor

web/src/lib/notes-client.ts

@@ -231,7 +231,11 @@ export async function listNoteVersions(
 
 export async function seedOnboardingWorkspace(): Promise<{ workspaceId: string; noteIds: string[] }> {
   const api = createNotesApiClient();
-  return api.fetch("/workspaces/onboarding-seed", { method: "POST", body: JSON.stringify({}) });
+  return api.fetch("/workspaces/onboarding-seed", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({}),
+  });
 }
 
 export async function chatOverWorkspace(workspaceId: string, message: string): Promise<{