chore(deploy): publish :staging image tag for CF Containers

Adds :staging alongside the existing :version and :latest tags so every
master push produces a staging-ready image that the CF Containers
staging environment can pull
(see infra/wrangler/worker/wrangler.toml).

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

Author: mastermanas805

.github/workflows/deploy.yml

@@ -147,6 +147,7 @@ jobs:
             --build-arg VERSION="${{ steps.meta.outputs.version }}" \
             -t "${IMAGE_REPO}:${{ steps.meta.outputs.version }}" \
             -t "${IMAGE_REPO}:latest" \
+            -t "${IMAGE_REPO}:staging" \
             --push \
             .