chore(deploy): drop the stale v6 surfer dependency and the gh-pages workflow

The publish workflow now deploys with `npx --yes @cloudron/surfer@7.2.0`
(pinned) and the v6 `put` command it replaced no longer exists, so
`cloudron-surfer@6` in devDependencies was dead weight in every `npm ci`.

Removing it also drops 35 packages that only existed for its bundled admin
UI (monaco-editor, three, openid-client, ejs, webdav-server, ...). Only those
entries are removed from package-lock.json - no re-resolution, so the diff is
pure deletion.

`.github/workflows/publish.yml` is the pre-Cloudron deploy path: it pushes the
build to a `gh-pages` branch with a third-party action and a `DCSITE` secret.
The site is published by surfer from `.gitea/workflows/publish.yml`, so this
file describes a deploy that cannot run and only misleads a reader looking for
how the site goes live.

Verified locally: `npm ci --legacy-peer-deps` (lock still in sync),
`npm run build` (136 pages), `npm run typecheck` clean, `npm run lint` reports
the same 8 pre-existing files as main and no new ones.

package.json

@@ -55,7 +55,6 @@
     "@types/react": "^18.3.31",
     "@types/react-dom": "^18.3.7",
     "bootstrap": "^5.0.0-beta3",
-    "cloudron-surfer": "^6.4.1",
     "jquery": "^3.6.0",
     "typescript": "^7.0.2"
   },