feat: F5.1 server F keeps the shared documents

A new package, packages/server: Hocuspocus 3.4.4 on /sync, a project a
document, refused with a reason when the store has not got it; every update
stored in Postgres as it comes and compacted after 500 updates, a minute of
quiet and when the last person leaves (FOR UPDATE on the row written when
the project is made); the janitor runs only here, at loading and 250 ms
after a change that is not its own; readers change nothing; /healthz; JSON
log. On closing it takes no one new and closes the sockets too (Hocuspocus'
close is a message after which a client signs in again on the same socket).
The tests use real clients against a throwaway Postgres in Docker.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/server/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "@mdg-filius/server",
+  "version": "0.0.0",
+  "private": true,
+  "license": "GPL-3.0-only",
+  "type": "module",
+  "exports": {
+    ".": "./src/index.ts"
+  },
+  "scripts": {
+    "build": "esbuild src/main.ts --bundle --platform=node --format=esm --target=node20 --outfile=dist/main.mjs --external:pg-native --banner:js=\"import { createRequire } from 'node:module'; const require = createRequire(import.meta.url);\"",
+    "start": "node dist/main.mjs"
+  },
+  "dependencies": {
+    "@hocuspocus/server": "3.4.4",
+    "@mdg-filius/core": "0.0.0",
+    "@mdg-filius/doc": "0.0.0",
+    "@mdg-filius/protocol": "0.0.0",
+    "@mdg-filius/sim": "0.0.0",
+    "pg": "8.23.1",
+    "ws": "8.22.0",
+    "y-protocols": "1.0.6",
+    "yjs": "^13.6.33"
+  },
+  "devDependencies": {
+    "@hocuspocus/provider": "3.4.4",
+    "@types/pg": "8.23.1",
+    "@types/ws": "8.18.2"
+  }
+}