feat(dashboard): add page export/import functionality

- ExportPageAction: exports page with SEO and section path as JSON
- ImportPageAction: imports page from JSON, resolves section by slug path
- PageController: export/download and import endpoints
- Routes: GET /{page}/export, POST /import
- Index.vue: export button per row, import button in header (local only)
- Import restricted to APP_ENV=local (backend + frontend check)

app/Containers/Dashboard/Actions/Pages/ExportPageAction.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace App\Containers\Dashboard\Actions\Pages;
+
+use App\Containers\AppStructure\Models\Page;
+
+class ExportPageAction
+{
+    public function run(Page $page): array
+    {
+        $page->load(['section.mainSection', 'seo']);
+
+        $sectionPath = null;
+
+        if ($page->section) {
+            $sectionPath = [
+                'main_section_slug' => $page->section->mainSection?->slug,
+                'sub_section_slug' => $page->section->slug,
+            ];
+        }
+
+        return [
+            'export_version' => 1,
+            'exported_at' => now()->toIso8601String(),
+            'page' => [
+                'title' => $page->title,
+                'slug' => $page->slug,
+                'code' => $page->code,
+                'content' => $page->content,
+                'settings' => $page->settings,
+                'searchable' => $page->searchable,
+                'sort' => $page->sort,
+                'is_visible' => $page->is_visible,
+            ],
+            'seo' => $page->seo ? [
+                'title' => $page->seo->title,
+                'description' => $page->seo->description,
+            ] : null,
+            'section_path' => $sectionPath,
+        ];
+    }
+}