feat: implement client header and navigation (E2.S3)

Epic 2 - Cliëntenbeheer: Complete Level 2 navigation structure with
context-aware header and sidebar for patient dossier.

E2.S3 - Cliënt Header & Nav:
- Create ClientHeader component showing:
  * Full patient name with prefix support
  * Color-coded status badge (screening/actief/afgerond/afgemeld)
  * Last modified timestamp (Dutch format)
  * John Doe indicator badge
  * Patient ID (subtle display)
- Create ClientSidebar navigation component with:
  * Back button to patient list
  * Navigation items for all tabs (always visible)
  * Active state highlighting
  * Icon support for each tab
- Create patient detail layout wrapper:
  * Combines header and sidebar
  * Full-height flex layout
  * Scrollable main content area
- Update patient detail page to dashboard view:
  * Quick action cards for Basisgegevens, Screening, Intake
  * Next steps guide for workflow
  * Remove old edit-only view
- Create Basisgegevens tab page:
  * Patient form for editing
  * John Doe warning for incomplete registrations
  * Pre-populated with existing data
- Create placeholder pages for future epics:
  * Screening (Epic 3)
  * Intake (Epic 4)
  * Diagnose (Epic 6)
  * Behandelplan (future)
  * Rapportage (future)

Technical implementation:
- app/epd/patients/[id]/components/client-header.tsx: New
- app/epd/patients/[id]/components/client-sidebar.tsx: New
- app/epd/patients/[id]/layout.tsx: New
- app/epd/patients/[id]/page.tsx: Completely rewritten as dashboard
- app/epd/patients/[id]/basisgegevens/page.tsx: New
- app/epd/patients/[id]/screening/page.tsx: New placeholder
- app/epd/patients/[id]/intake/page.tsx: New placeholder
- app/epd/patients/[id]/diagnose/page.tsx: New placeholder
- app/epd/patients/[id]/behandelplan/page.tsx: New placeholder
- app/epd/patients/[id]/rapportage/page.tsx: New placeholder
- docs/specs/screening-intake/bouwplan-screening-intake-v1.0.md: Updated

Epic 2 is now complete with all 3 stories implemented!

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/epd/patients/[id]/screening/page.tsx

@@ -0,0 +1,40 @@
+/**
+ * Screening Page
+ * E2.S3: Placeholder for screening functionality (to be implemented in Epic 3)
+ */
+
+import { ClipboardList } from 'lucide-react';
+
+export default async function ScreeningPage({
+  params,
+}: {
+  params: Promise<{ id: string }>;
+}) {
+  const { id } = await params;
+
+  return (
+    <div className="p-6">
+      {/* Page Header */}
+      <div className="mb-6">
+        <h2 className="text-lg font-semibold text-slate-900">Screening</h2>
+        <p className="text-sm text-slate-600 mt-1">
+          Activiteitenlog, documenten, hulpvraag en screeningsbesluit
+        </p>
+      </div>
+
+      {/* Placeholder */}
+      <div className="bg-white rounded-lg border border-slate-200 p-12 text-center">
+        <div className="inline-flex items-center justify-center w-16 h-16 rounded-full bg-amber-50 mb-4">
+          <ClipboardList className="h-8 w-8 text-amber-500" />
+        </div>
+        <h3 className="text-lg font-semibold text-slate-900 mb-2">
+          Screening Module - Coming Soon
+        </h3>
+        <p className="text-sm text-slate-600 max-w-md mx-auto">
+          De screening functionaliteit wordt geïmplementeerd in Epic 3. Dit omvat
+          activiteitenlog, documentbeheer, hulpvraag registratie en screeningsbesluit.
+        </p>
+      </div>
+    </div>
+  );
+}