fix(ui): host .repo files and use URL form in install instructions

The previous instructions used `--from-repofile=/dev/stdin` with a
heredoc, which fails because dnf copies the source file and /dev/stdin
is not a regular file. Host the .repo files on the deployed site and
update the docs to use `--from-repofile=https://...` instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/deploy-ui.yml

@@ -46,6 +46,7 @@ jobs:
             --delete \
             --chmod D755,F644 \
             --include="index.html" \
+            --include="*.repo" \
             --include="assets/***" \
             --exclude="*" \
             ui/dist/ \