ci: drop cache: setting in setup-go/setup-node

`cache: true` (setup-go) and `cache: pnpm` (setup-node) make the
actions push and pull tarballs through the Gitea Actions cache
service at 192.168.0.222:43513. That endpoint currently does not
answer, so every workflow burns minutes per run on reserveCache
retries before the action gives up.

In host-mode the real caches live under the runner user's $HOME
(~/go/pkg/mod, ~/.cache/go-build, ~/.local/share/pnpm,
~/.cache/ms-playwright) and persist between jobs without any
actions/cache plumbing. Switching cache: off avoids the zombie
retries and uses the local disk caches the runner already has warm.

Reviving the cache service is a separate TODO. Until then this is
the simpler and faster baseline.

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

.gitea/workflows/prod-build.yaml

@@ -37,7 +37,8 @@ jobs:
         uses: actions/setup-go@v5
         with:
           go-version-file: go.work
-          cache: true
+          # See go-unit.yaml for why `cache: true` is disabled.
+          cache: false
 
       - name: Set up pnpm
         uses: pnpm/action-setup@v4
@@ -48,8 +49,7 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: 22
-          cache: pnpm
-          cache-dependency-path: ui/pnpm-lock.yaml
+          # See dev-deploy.yaml for why `cache: pnpm` is disabled.
 
       - name: Resolve image tag
         id: tag