feat(server): port the UO models, utils and schema fragment

The data half of the extraction: 8 model directories, 13 utils, the shard
stream catalog and the 27-table schema fragment with its purge.

server/core.js is what makes the port a one-line import change per file rather
than a signature change per function. Ported code requires its dependencies at
file scope -- `const { query } = require('../../core')` -- which runs before
register() has been called and before any ctx exists. So every member is a
stable function that resolves ctx when CALLED, and nothing may be destructured
off ctx at init either, because core is free to hand over a getter.

Two helpers are vendored rather than taken from ctx, and the line between them
is the point. utils/excerpt.js is core's deriveExcerpt -- nine lines of pure
text handling. Core's sanitiser next to it was NOT copied: a second copy of a
security control diverges silently the moment either is fixed. announceLinks.js
vendors legError and articleUrl the same way, but baseUrl could not be: core's
reads APP_BASE_URL, and §2.7 forbids a module reading core's environment, so it
comes off ctx.site.baseUrl.

The schema fragment is core's 27 shard_*/uo_link_* statements, verbs CREATE,
ALTER and UPDATE only, every CREATE TABLE guarded. Two of its tables carry a
foreign key INTO users, which is allowed and is why the replay order matters --
core's schema is in place before this runs. The reverse never occurs and must
not: it would make core unable to boot without a module installed.

One real port bug caught by the integration run, not by tests: the atlas art
map resolved `../../../db/data`, which pointed at core's tree when this file
lived there and points outside server/ now. A path that happens to resolve is
exactly what survives a green suite, because the absent-file branch returns {}
and looks like the normal case.

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

server/package-lock.json

@@ -8,6 +8,9 @@
       "name": "module-uo-server",
       "version": "0.1.0",
       "license": "GPL-3.0-or-later",
+      "dependencies": {
+        "ws": "^8.21.0"
+      },
       "devDependencies": {
         "express": "^4.19.2",
         "express-validator": "^7.2.0"
@@ -927,6 +930,27 @@
       "engines": {
         "node": ">= 0.8"
       }
+    },
+    "node_modules/ws": {
+      "version": "8.21.3",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-8.21.3.tgz",
+      "integrity": "sha512-201TZ/kPWxoPr/OKWjquZR1SWKXcvxdH+e1xrx89b3YbmzLMFCLfnaG1HFIgWzJOEWZ7MvpK++odZufgYR50Rw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=10.0.0"
+      },
+      "peerDependencies": {
+        "bufferutil": "^4.0.1",
+        "utf-8-validate": ">=5.0.2"
+      },
+      "peerDependenciesMeta": {
+        "bufferutil": {
+          "optional": true
+        },
+        "utf-8-validate": {
+          "optional": true
+        }
+      }
     }
   }
 }