feat: improve infrastructure security

[Kuruyia]

This improves the overall security of the project by doing the following:

• Sign the container images that are pushed to GHCR via the CI
• Add an image signature verification policy in Kubernetes
• Run the microservices as a non-root user in the containers
• Drop privileges in the Kubernetes deployments
• Configure resource limits for the containers in Kubernetes
• Configure network policies in Kubernetes

Other changes

The dorny/paths-filter action in the CI has been updated to v3.