feat(membership): print button + print-optimized CSS for declarations

- Blue "Drukuj deklarację" button in action sidebar (submitted + under_review)
- @media print CSS: hides nav, sidebar, buttons; full-width main content
- Print header with chamber name, declaration number, date, status
- Clean data sections for paper output
- Uses native window.print() — browser shows printer selection dialog

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/admin/membership_detail.html

@@ -537,10 +537,56 @@
         background: var(--background);
         border-radius: var(--radius);
     }
+
+    /* Print styles */
+    @media print {
+        /* Hide navigation, sidebar actions, admin bar, buttons, modals */
+        nav, .admin-bar, .sidebar, .action-buttons, .action-help,
+        .modal, .modal-overlay, .alert, .btn-action, .btn-back,
+        footer, .notifications-menu, .user-menu, .breadcrumb,
+        .workflow-timeline, .detail-header .status-badge { display: none !important; }
+
+        /* Full width for main content */
+        .content-grid { display: block !important; }
+        .main-content { width: 100% !important; max-width: 100% !important; }
+
+        /* Clean print header */
+        body { font-size: 11pt; color: #000; background: #fff; }
+        .detail-header h1 { font-size: 16pt; margin-bottom: 4pt; }
+
+        /* Print header with logo and title */
+        .print-header {
+            display: block !important;
+            text-align: center;
+            margin-bottom: 20pt;
+            padding-bottom: 10pt;
+            border-bottom: 2px solid #2E4872;
+        }
+        .print-header h2 { font-size: 14pt; color: #2E4872; margin: 0; }
+        .print-header p { font-size: 10pt; color: #666; margin: 4pt 0 0; }
+
+        /* Data sections clean */
+        .info-section { break-inside: avoid; margin-bottom: 12pt; border: 1px solid #ddd; padding: 8pt; }
+        .info-section h2 { font-size: 12pt; color: #2E4872; border-bottom: 1px solid #2E4872; padding-bottom: 4pt; }
+        .info-row { padding: 2pt 0; }
+        .info-label { font-weight: bold; }
+
+        /* Page setup */
+        @page { margin: 15mm; }
+    }
+
+    /* Hidden in screen, visible in print */
+    .print-header { display: none; }
 </style>
 {% endblock %}
 
 {% block content %}
+<div class="print-header">
+    <h2>Izba Gospodarcza Norda Biznes</h2>
+    <p>Deklaracja członkowska nr {{ application.id }} — {{ application.company_name }}</p>
+    <p>Data złożenia: {{ application.submitted_at.strftime('%d.%m.%Y, %H:%M') if application.submitted_at else 'brak' }} | Status: {{ application.status_label }}</p>
+</div>
+
 <a href="{{ url_for('admin.admin_membership') }}" class="back-link">
     ← Powrót do listy deklaracji
 </a>
@@ -777,6 +823,9 @@
                 <button class="btn-action btn-review" onclick="startReview()">
                     Rozpocznij rozpatrywanie
                 </button>
+                <button class="btn-action" onclick="window.print()" style="background: var(--primary); color: white; margin-top: 8px;">
+                    🖨 Drukuj deklarację
+                </button>
             </div>
             <p class="action-help">
                 Zmieni status na "W trakcie rozpatrywania" i odblokuje opcje zatwierdzenia, odrzucenia lub prośby o poprawki.
@@ -822,6 +871,9 @@
                 <button class="btn-action btn-reject" onclick="openRejectModal()">
                     ✗ Odrzuć
                 </button>
+                <button class="btn-action" onclick="window.print()" style="background: var(--primary); color: white; margin-top: 8px;">
+                    🖨 Drukuj deklarację
+                </button>
             </div>
 
             <div class="form-group" style="margin-top: var(--spacing-lg);">