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>

Dockerfile

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+FROM python:3.12-slim
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PIP_DISABLE_PIP_VERSION_CHECK=1 \
+    SITEFORGE_DATA_DIR=/data
+WORKDIR /opt/siteforge
+COPY requirements.txt ./
+RUN pip install --no-cache-dir -r requirements.txt && \
+    groupadd -g 10001 siteforge && useradd -u 10001 -g 10001 -s /usr/sbin/nologin siteforge && \
+    mkdir -p /data /published && chown -R siteforge:siteforge /data /published
+COPY --chown=siteforge:siteforge app/ ./app/
+COPY --chown=siteforge:siteforge themes/ ./themes/
+COPY --chown=siteforge:siteforge examples/ ./examples/
+USER siteforge
+EXPOSE 8787
+HEALTHCHECK --interval=30s --timeout=5s --start-period=25s --retries=3 CMD python -c "import urllib.request; urllib.request.urlopen('http://127.0.0.1:8787/api/health', timeout=3)"
+CMD ["python","-m","uvicorn","app.main:app","--host","0.0.0.0","--port","8787","--proxy-headers"]