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>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "epicure",
-  "version": "0.51.2",
+  "version": "0.51.3",
   "private": true,
   "scripts": {
     "dev": "pnpm --filter web dev",