Fix: Align exporter labels, image tags, and build process

- Helm Chart:
  - Added `app.kubernetes.io/component: exporter` to the exporter pod
    labels via `values.yaml` to match the service selector.
  - Updated image tag defaulting in `exporter-controller.yaml` to use
    `Chart.appVersion` directly (e.g., "0.1.0" instead of "v0.1.0").

- Build Process (`.github/workflows/release.yml`):
  - Configured `docker/metadata-action` to ensure image tags are generated
    without a 'v' prefix (e.g., "0.1.0" from Git tag "v0.1.0").
    This aligns the published image tags with the Helm chart's
    updated image tag references.

- Repository:
  - Added `rendered-manifests.yaml` and `rendered-manifests-updated.yaml`
    to `.gitignore`.

.gitignore

@@ -37,3 +37,7 @@ Thumbs.db
 # Helm
 !charts/iperf3-monitor/.helmignore
 charts/iperf3-monitor/charts/
+
+# Rendered Kubernetes manifests (for local testing)
+rendered-manifests.yaml
+rendered-manifests-updated.yaml