chore: import SiteForge Factory V5 source (baseline)

导入 SiteForge Factory V5 基线源码：
- FastAPI + SQLite + Docker Compose（Web + Worker）架构
- 四套商业主题 × 14 页面模板（1.1.0，含历史版本快照）
- 四种建站模式骨架 + 迁移审计 + 发布门禁
- 52 项 pytest 测试
- 补全计划主文档 docs/superpowers/plans/

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

requirements.txt

@@ -0,0 +1,14 @@
+# Runtime versions are pinned so Docker rebuilds do not silently select a new
+# framework generation. Update these deliberately and run scripts/check.ps1.
+fastapi==0.141.1
+starlette==1.4.1
+pydantic==2.13.4
+uvicorn[standard]==0.52.1
+jinja2==3.1.6
+python-multipart==0.0.32
+httpx==0.28.1
+beautifulsoup4==4.15.0
+bleach==6.4.0
+defusedxml==0.7.1
+openpyxl==3.1.5
+itsdangerous==2.2.0