fix(docs): repair the escaped apostrophes, and document this module's env vars

Nineteen `#swagger` descriptions carried a `\'` inside a single-quoted string.
That is correct JavaScript and wrong here: swagger-autogen does not evaluate the
annotation as JS, so the backslash survives into the spec and Swagger UI renders
"the shard\'s published ruleset" to a reader. Replaced with a typographic
apostrophe, which the same files already use elsewhere.

Found by opening /api/docs in a browser against a real core with this module
installed — the fragment was valid JSON, the paths were right, every test passed,
and it was still wrong on screen. Nothing that reads the artifact can see this;
only reading the rendered page can.

Also documents the four environment variables this module reads
(UOLINK_BASE_URL / _WS_URL / _PROTOCOL, TOWNCRIER_DURATION_SEC). Core's
.env.example is dropping them in the paired website PR: they were never core's,
and a half-copy in two repos goes stale silently.

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

server/router/admin/uoLink.router.js

@@ -70,7 +70,7 @@ uoLinkRouter.get(
   '/signup-mode',
   // #swagger.tags = ['Admin · Shard']
   // #swagger.summary = 'Get the game-account signup mode (admin only)'
-  // #swagger.description = 'Whether the site offers game-account creation, and in which direction. The shard\'s own SignupMode (Bridge.cfg) must agree: website/hybrid accept site-created accounts, game refuses them.'
+  // #swagger.description = 'Whether the site offers game-account creation, and in which direction. The shard’s own SignupMode (Bridge.cfg) must agree: website/hybrid accept site-created accounts, game refuses them.'
   // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
   /* #swagger.responses[200] = { description: 'The configured mode and the legal values', content: { "application/json": { schema: { type: "object", properties: { mode: { type: "string" }, modes: { type: "array", items: { type: "string" } } } } } } } */
   /* #swagger.responses[403] = { description: 'Admin role required', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */