feat(mcp-docugen): scaffold service + Docker stack con gateway Caddy

Task 0 del piano (adattato a workspace uv):
- services/mcp-docugen/: pyproject.toml, src/mcp_docugen/, tests/unit+integration/,
  README, .env.example. Package rinominato da docugen_mcp -> mcp_docugen.
- Root pyproject.toml: aggiunto services/mcp-docugen a workspace members.
- .python-version: 3.11
- uv.lock committato.

Docker stack stile CerberoSuite/Cerbero con prefisso "arca-":
- docker/base.Dockerfile -> arca-base:latest
- docker/mcp-docugen.Dockerfile -> arca-mcp-docugen:dev (porta interna 9100,
  label arca.service, runtime multi-stage, user non-root, healthcheck)
- docker-compose.yml root: gateway Caddy unica porta host (8080) + mcp-docugen
  su rete interna. Security defaults cap_drop ALL, no-new-privileges, read_only
  ove applicabile, restart unless-stopped.
- gateway/Caddyfile: reverse proxy /mcp-docugen/* -> mcp-docugen:9100 + landing.
- gateway/public/index.html: landing page minimale.

.env.example root aggiornato con DOCUGEN_API_KEY + OPENROUTER_API_KEY condivisa.

Task 1-12 (implementazione TDD effettiva) ancora da fare.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/mcp-docugen/pyproject.toml

@@ -0,0 +1,40 @@
+[project]
+name = "mcp-docugen"
+version = "0.1.0"
+description = "MCP server for document generation from Markdown templates via OpenRouter"
+requires-python = ">=3.11"
+dependencies = [
+    "mcp>=1.2",
+    "fastapi>=0.115",
+    "uvicorn[standard]>=0.34",
+    "pydantic>=2.0",
+    "pydantic-settings>=2.0",
+    "httpx>=0.27",
+    "aiosqlite>=0.20",
+    "aiofiles>=24.0",
+    "pyyaml>=6.0",
+    "pillow>=11.0",
+    "python-multipart>=0.0.9",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.0",
+    "pytest-asyncio>=0.24",
+    "respx>=0.21",
+    "pytest-cov>=5.0",
+]
+
+[project.scripts]
+mcp-docugen = "mcp_docugen.main:run"
+
+[tool.coverage.run]
+source = ["src/mcp_docugen"]
+omit = ["src/mcp_docugen/main.py"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/mcp_docugen"]