docs: spell out Gitea integration setup in admin Settings UI (v0.51.3)

GITEA_URL/GITEA_REPO format and the exact token scope needed (issue
read+write only) were only in the commit message and CLAUDE session —
now visible right above the fields admins are filling in.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/admin/settings/page.tsx

@@ -13,7 +13,13 @@ const SETTING_GROUPS = [
   },
   {
     title: "Gitea Integration",
-    description: "Support tickets submitted in-app automatically open an issue on this Gitea repo. Token needs issue read/write scope on the target repo.",
+    description:
+      "Support tickets submitted in-app automatically open an issue on this Gitea repo. Setup: " +
+      "GITEA_URL = your Gitea base URL, no trailing slash (e.g. https://git.example.com). " +
+      "GITEA_REPO = owner/repo (e.g. owner/my-app). " +
+      "GITEA_TOKEN = a personal access token — Gitea → Settings → Applications → Generate New Token — " +
+      "with the \"issue\" scope (read + write) only; nothing broader is needed since this integration " +
+      "never touches code or repo settings, just creates issues.",
     keys: ["GITEA_URL", "GITEA_TOKEN", "GITEA_REPO"] as const,
   },
 ];