feat(admin/ui): enterprise inquiries pipeline

Add /enterprise page wired to /admin/enterprise/inquiries. Sales-style
pipeline: pending → contacted → converted | declined, with an inline
<select> on each row so triage is one click per inquiry rather than a
detail-page round-trip.

Each row shows company, contact, estimated volume, team size, and the
free-form notes from the marketing-site form. Pending is the default
filter so the queue surfaces first; "All" reveals historical decisions.

Added a sidebar entry under Accounts (Briefcase icon) so the inquiry
queue is one click away from the rest of the customer-facing admin.

admin/src/lib/api/client/admin/enterprise.ts

@@ -0,0 +1,41 @@
+// /admin/enterprise/inquiries — sales-pipeline triage.
+
+import { Request } from "@/lib/api/client";
+import type {
+    EnterpriseInquiry,
+    UpdateEnterpriseInquiryRequest,
+} from "@/lib/api/models/admin";
+
+export function listEnterpriseInquiries(
+    status?: string,
+    limit = 50,
+): Promise<{ data: EnterpriseInquiry[] }> {
+    const usp = new URLSearchParams();
+    if (status) usp.set("status", status);
+    usp.set("limit", String(limit));
+    return Request({
+        method: "GET",
+        url: `/admin/enterprise/inquiries?${usp.toString()}`,
+        authorization: true,
+    });
+}
+
+export function getEnterpriseInquiry(id: string): Promise<EnterpriseInquiry> {
+    return Request({
+        method: "GET",
+        url: `/admin/enterprise/inquiries/${id}`,
+        authorization: true,
+    });
+}
+
+export function updateEnterpriseInquiry(
+    id: string,
+    body: UpdateEnterpriseInquiryRequest,
+): Promise<EnterpriseInquiry> {
+    return Request({
+        method: "PATCH",
+        url: `/admin/enterprise/inquiries/${id}`,
+        authorization: true,
+        data: body,
+    });
+}

admin/src/lib/api/models/admin.ts

@@ -323,6 +323,35 @@ export interface ProvisioningJobCreate {
     };
 }
 
+// /admin/enterprise/inquiries — sales pipeline for "talk to us"
+// requests submitted from the marketing site.
+
+export type EnterpriseInquiryStatus =
+    | "pending"
+    | "contacted"
+    | "converted"
+    | "declined";
+
+export interface EnterpriseInquiry {
+    id: string;
+    company_name: string;
+    contact_name: string;
+    contact_email: string;
+    estimated_volume?: number | null;
+    team_size?: number | null;
+    notes: string;
+    status: EnterpriseInquiryStatus;
+    created_at: string;
+    processed_at?: string | null;
+    processed_by?: string | null;
+}
+
+export interface UpdateEnterpriseInquiryRequest {
+    status?: EnterpriseInquiryStatus;
+    assigned_to?: string;
+    notes?: string;
+}
+
 // /admin/campaigns/* — platform-wide campaign admin (force-stop runaway
 // campaigns, inspect engagement counters per campaign).