feat(lead-gen): shared field options, work-email validation, and submit seam

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ui/src/components/lead-forms/submitLead.ts

@@ -0,0 +1,31 @@
+// Single submission seam for all lead forms.
+// Today: fires a PostHog capture. Later: add a POST to the backend
+// (MongoDB) endpoint here — no form component will need to change.
+
+import posthog from "posthog-js";
+
+import { PostHogEvent } from "@/constants/posthog-events";
+
+import type { LeadKind, LeadSource } from "./leadFieldOptions";
+
+const SUBMIT_EVENT: Record<LeadKind, string> = {
+  topup: PostHogEvent.TOPUP_REQUESTED,
+  hire_expert: PostHogEvent.HIRE_EXPERT_SUBMITTED,
+  enterprise: PostHogEvent.ENTERPRISE_LEAD_SUBMITTED,
+};
+
+export interface SubmitLeadArgs {
+  kind: LeadKind;
+  source: LeadSource;
+  // Field values, already validated by the caller. Non-sensitive lead data.
+  payload: Record<string, unknown>;
+}
+
+export async function submitLead({ kind, source, payload }: SubmitLeadArgs): Promise<void> {
+  // PostHog capture — the durable record until the backend endpoint lands.
+  posthog.capture(SUBMIT_EVENT[kind], { source, ...payload });
+
+  // FUTURE: when the MongoDB endpoint exists, POST here, e.g.
+  //   const res = await submitLeadApiV1LeadsPost({ body: { kind, source, ...payload } });
+  //   if (res.error) throw new Error(detailFromError(res.error, "Failed to submit"));
+}