feat(10-redo-C): CRM leads module — schema, services, UI (Phase 10 redo)

Stage C of staged Phase 10 redo. Restores dangling phase10-wip work:
- schema.ts: leads expansion + activities/reminders tables + relations
- lead-service.ts / lead-validators.ts service layer
- /admin/leads list + detail + actions, LeadTable/LeadDetail/LeadForm
- LogActivityModal, SendQuoteModal, FollowUpWidget on dashboard
- migration 0005 (applied to prod DB in Stage B, along with
  previously-missing 0001/0003/0004 — root cause of all post-deploy
  500s: prod DB had no migrations applied since 0000)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/app/admin/page.tsx

@@ -1,4 +1,6 @@
+import { Suspense } from "react";
 import { getDashboardStats } from "@/lib/dashboard-queries";
+import { FollowUpWidget } from "@/components/admin/dashboard/FollowUpWidget";
 import { Users, FolderOpen, Euro, Clock } from "lucide-react";
 
 export const revalidate = 0;
@@ -59,6 +61,13 @@ export default async function AdminDashboard() {
     <div className="max-w-5xl">
       <h1 className="text-2xl font-bold text-gray-900 mb-6">Dashboard</h1>
 
+      {/* Follow-up Widget */}
+      <div className="mb-8">
+        <Suspense fallback={<div className="animate-pulse h-40 bg-gray-200 rounded-lg" />}>
+          <FollowUpWidget />
+        </Suspense>
+      </div>
+
       {/* KPI cards */}
       <div className="grid grid-cols-2 lg:grid-cols-4 gap-4 mb-8">
         <KpiCard