chore: organize repo as uv workspace multi-MCP monorepo

Layout stile CerberoSuite/Cerbero:
- services/ per MCP workspace members (futuri: mcp-docugen, mcp-convert, mcp-inbox)
- docs/ flat con design+implementation per componente
- scripts/, secrets/ placeholder
- pyproject.toml root (uv workspace vuoto + ruff + pytest)
- .gitignore, .env.example, .mcp.json.example, README.md

Rinominate le doc: Docs/<comp>/2026-04-21-*.md -> docs/<comp>-*.md.

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

.mcp.json.example

@@ -0,0 +1,9 @@
+{
+  "mcpServers": {
+    "docugen": {
+      "type": "http",
+      "url": "https://docugen.<dominio>/mcp",
+      "headers": { "Authorization": "Bearer <API_KEY>" }
+    }
+  }
+}