补充测试覆盖率 + 新增部署引导命令 bootstrap_deployment

- 新增 apps/blog、apps/solutions、apps/home、apps/api 测试文件，覆盖标签/排序/
  草稿过滤、HomePage.subpage_types 回归测试、page_preview 预览接口
- apps/core/tests.py 新增健康检查端点、发布 webhook 信号、bootstrap_deployment
  命令的测试用例，pytest 用例数从 40 增至 65，全部通过
- 修复 apps/api/urls.py 中 PagePreviewAPIViewSet.get_object() 未捕获
  DoesNotExist 导致 500 而非文档承诺 404 的 bug
- 新增 apps/core/management/commands/bootstrap_deployment.py：部署时按环境变量
  幂等创建首个超级管理员账号并联动初始化 RBAC 权限组，.env.example 补充对应
  环境变量说明
- 新增 OpenSearch + 中文分词本地 PoC 脚手架（docker-compose.opensearch.yml +
  docker/opensearch/Dockerfile），调研结论详见设计文档 §2.10
- 更新设计文档 §2.16 Phase 1 进度清单

apps/solutions/tests.py

@@ -0,0 +1,39 @@
+"""apps.solutions 单元测试：页面树结构与列表上下文（与 apps.products/apps.cases 同构）。"""
+import pytest
+
+from apps.solutions.models import SolutionIndexPage, SolutionPage
+
+pytestmark = pytest.mark.django_db
+
+
+@pytest.fixture
+def solution_index(home_page):
+    index = SolutionIndexPage(title="解决方案", slug="solutions", intro="行业解决方案")
+    home_page.add_child(instance=index)
+    return index
+
+
+def test_solution_page_can_be_created_under_index(solution_index):
+    solution = SolutionPage(
+        title="制造业解决方案",
+        slug="manufacturing",
+        industry="制造业",
+        summary="面向制造业的数字化转型方案",
+    )
+    solution_index.add_child(instance=solution)
+
+    assert SolutionPage.objects.live().descendant_of(solution_index).count() == 1
+
+
+def test_solution_index_context_excludes_draft_solutions(solution_index):
+    live_solution = SolutionPage(title="方案 A", slug="solution-a")
+    solution_index.add_child(instance=live_solution)
+
+    draft_solution = SolutionPage(title="方案 B", slug="solution-b", live=False)
+    solution_index.add_child(instance=draft_solution)
+
+    context = solution_index.get_context(request=None)
+    titles = [s.title for s in context["solutions"]]
+
+    assert "方案 A" in titles
+    assert "方案 B" not in titles