feat:E-Sign 템플릿 관리 시스템 Phase 2 구현

- 템플릿 관리 전용 페이지 (카드 그리드, 검색/필터, 편집/복제/삭제)
- API: showTemplate, updateTemplate, duplicateTemplate 추가
- indexTemplates에 category/search 필터 추가
- 계약 생성 시 템플릿 선택 UI 추가
- 필드 에디터에서 URL 파라미터 template_id 자동 적용
- EsignFieldTemplate 모델에 category 필드 추가

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Http/Controllers/ESign/EsignApiController.php

@@ -363,14 +363,19 @@ public function indexTemplates(Request $request): JsonResponse
     {
         $tenantId = session('selected_tenant_id', 1);
         $query = EsignFieldTemplate::forTenant($tenantId)
-            ->where('is_active', true)
-            ->with('items');
+            ->where('is_active', true);
 
+        if ($category = $request->input('category')) {
+            $query->where('category', $category);
+        }
+        if ($search = $request->input('search')) {
+            $query->where('name', 'like', "%{$search}%");
+        }
         if ($signerCount = $request->input('signer_count')) {
             $query->where('signer_count', $signerCount);
         }
 
-        $templates = $query->orderBy('created_at', 'desc')->get();
+        $templates = $query->withCount('items')->with('creator:id,name')->latest()->get();
 
         return response()->json(['success' => true, 'data' => $templates]);
     }
@@ -383,6 +388,7 @@ public function storeTemplate(Request $request): JsonResponse
         $request->validate([
             'name' => 'required|string|max:100',
             'description' => 'nullable|string',
+            'category' => 'nullable|string|max:50',
             'items' => 'required|array|min:1',
             'items.*.signer_order' => 'required|integer|min:1',
             'items.*.page_number' => 'required|integer|min:1',
@@ -406,6 +412,7 @@ public function storeTemplate(Request $request): JsonResponse
                 'tenant_id' => $tenantId,
                 'name' => $request->input('name'),
                 'description' => $request->input('description'),
+                'category' => $request->input('category'),
                 'signer_count' => $signerCount,
                 'is_active' => true,
                 'created_by' => auth()->id(),
@@ -437,6 +444,95 @@ public function storeTemplate(Request $request): JsonResponse
         ]);
     }
 
+    /**
+     * 템플릿 단건 조회
+     */
+    public function showTemplate(int $id): JsonResponse
+    {
+        $tenantId = session('selected_tenant_id', 1);
+        $template = EsignFieldTemplate::forTenant($tenantId)
+            ->where('is_active', true)
+            ->with(['items', 'creator:id,name'])
+            ->findOrFail($id);
+
+        return response()->json(['success' => true, 'data' => $template]);
+    }
+
+    /**
+     * 템플릿 메타데이터 수정
+     */
+    public function updateTemplate(Request $request, int $id): JsonResponse
+    {
+        $request->validate([
+            'name' => 'required|string|max:100',
+            'description' => 'nullable|string',
+            'category' => 'nullable|string|max:50',
+        ]);
+
+        $tenantId = session('selected_tenant_id', 1);
+        $template = EsignFieldTemplate::forTenant($tenantId)->findOrFail($id);
+
+        $template->update([
+            'name' => $request->input('name'),
+            'description' => $request->input('description'),
+            'category' => $request->input('category'),
+        ]);
+
+        return response()->json([
+            'success' => true,
+            'message' => '템플릿이 수정되었습니다.',
+            'data' => $template->fresh()->load('creator:id,name'),
+        ]);
+    }
+
+    /**
+     * 템플릿 복제
+     */
+    public function duplicateTemplate(int $id): JsonResponse
+    {
+        $tenantId = session('selected_tenant_id', 1);
+        $template = EsignFieldTemplate::forTenant($tenantId)
+            ->where('is_active', true)
+            ->with('items')
+            ->findOrFail($id);
+
+        $newTemplate = DB::transaction(function () use ($template, $tenantId) {
+            $newTemplate = EsignFieldTemplate::create([
+                'tenant_id' => $tenantId,
+                'name' => $template->name . ' (복사)',
+                'description' => $template->description,
+                'category' => $template->category,
+                'signer_count' => $template->signer_count,
+                'is_active' => true,
+                'created_by' => auth()->id(),
+            ]);
+
+            foreach ($template->items as $item) {
+                EsignFieldTemplateItem::create([
+                    'template_id' => $newTemplate->id,
+                    'signer_order' => $item->signer_order,
+                    'page_number' => $item->page_number,
+                    'position_x' => $item->position_x,
+                    'position_y' => $item->position_y,
+                    'width' => $item->width,
+                    'height' => $item->height,
+                    'field_type' => $item->field_type,
+                    'field_label' => $item->field_label,
+                    'is_required' => $item->is_required,
+                    'sort_order' => $item->sort_order,
+                ]);
+            }
+
+            return $newTemplate;
+        });
+
+        return response()->json([
+            'success' => true,
+            'message' => '템플릿이 복제되었습니다.',
+            'data' => $newTemplate->load(['items', 'creator:id,name'])->loadCount('items'),
+        ]);
+    }
+
     /**
      * 템플릿 삭제 (soft: is_active=false)
      */