Add yq to forgejo-runner and replace sed YAML edits (#180)

## Summary
- Install yq in the forgejo-runner container image for structured YAML editing
- Replace fragile `sed` regex patterns with `yq` in `build-blumeops.yaml` and `cv-deploy.yaml` workflows

## Deployment
1. Merge this PR
2. Tag and release forgejo-runner v3.1.0: `mise run container-tag-and-release forgejo-runner v3.1.0`
3. Update runner label in `argocd/manifests/forgejo-runner/external-secret.yaml` from `v3.0.2` to `v3.1.0`
4. Sync the forgejo-runner app: `argocd app sync forgejo-runner`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/180

.forgejo/workflows/build-blumeops.yaml

@@ -234,7 +234,7 @@ jobs:
           RELEASE_URL="https://forge.ops.eblu.me/eblume/blumeops/releases/download/${VERSION}/${TARBALL}"
 
           echo "Updating $DEPLOYMENT_FILE with new release URL..."
-          sed -i "s|value: \"https://forge.ops.eblu.me/eblume/blumeops/releases/download/[^\"]*\"|value: \"${RELEASE_URL}\"|" "$DEPLOYMENT_FILE"
+          yq -i "(.spec.template.spec.containers[0].env[] | select(.name == \"DOCS_RELEASE_URL\")).value = \"${RELEASE_URL}\"" "$DEPLOYMENT_FILE"
 
           echo "Updated deployment:"
           grep -A1 "DOCS_RELEASE_URL" "$DEPLOYMENT_FILE"

.forgejo/workflows/cv-deploy.yaml

@@ -68,7 +68,7 @@ jobs:
           RELEASE_URL="https://forge.ops.eblu.me/api/packages/eblume/generic/cv/${VERSION}/${TARBALL}"
 
           echo "Updating $DEPLOYMENT_FILE with CV_RELEASE_URL..."
-          sed -i "s|value: \"https://forge.ops.eblu.me/api/packages/eblume/generic/cv/[^\"]*\"|value: \"${RELEASE_URL}\"|" "$DEPLOYMENT_FILE"
+          yq -i "(.spec.template.spec.containers[0].env[] | select(.name == \"CV_RELEASE_URL\")).value = \"${RELEASE_URL}\"" "$DEPLOYMENT_FILE"
 
           echo "Updated deployment:"
           grep -A1 "CV_RELEASE_URL" "$DEPLOYMENT_FILE"