feat: add envoy grpc route support

[andibeuge]

Summary

• add a common GRPCRoute helper and wire it into microservice and monolith charts
• add envoy.grpcRoutes defaults/examples and ReferenceGrant support
• update BackendTrafficPolicy targeting for GRPCRoute while preserving HTTPRoute behavior

Verification

• helm lint parcellab/common
• helm lint parcellab/microservice
• helm lint parcellab/monolith
• helm template smoke renders for GRPCRoute global and per-route BackendTrafficPolicy

[Copilot]

Pull request overview

This PR extends the shared common Helm library and wires it into the microservice and monolith charts to support Envoy Gateway GRPCRoute resources, including route-specific BackendTrafficPolicy generation and updated global BackendTrafficPolicy targeting logic.

Changes:

• Added a new shared common.grpcroutes helper to render Gateway API GRPCRoute resources with deterministic naming/labels and rollout-service backendRef rewriting.
• Introduced envoy.grpcRoutes defaults/examples in microservice and monolith, and updated ReferenceGrant defaults to allow GRPCRoute.
• Updated BackendTrafficPolicy rendering to support both HTTPRoute and GRPCRoute targets while preserving existing HTTP behavior.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
parcellab/common/Chart.yaml	Bumps library chart version for the new GRPCRoute support.
parcellab/common/templates/_backendtrafficpolicy.tpl	Generalizes route targeting to support multiple Gateway API route kinds and improves route-specific error paths.
parcellab/common/templates/_grpcroutes.tpl	Adds the shared GRPCRoute renderer used by application charts.
parcellab/common/templates/_httproutes.tpl	Extends global BackendTrafficPolicy targetRefs collection to include GRPCRoutes without changing HTTPRoute rendering.
parcellab/common/values.yaml	Adds envoy.grpcRoutes default key to the library values.
parcellab/microservice/Chart.yaml	Bumps chart version to ship GRPCRoute support.
parcellab/microservice/README.md	Documents GRPCRoute support under the Envoy resources section.
parcellab/microservice/templates/grpcroutes.yaml	Wires the new shared GRPCRoute helper into the microservice chart.
parcellab/microservice/values.yaml	Adds envoy.grpcRoutes defaults/examples and updates ReferenceGrant defaults for GRPCRoute.
parcellab/monolith/Chart.yaml	Bumps chart version to ship GRPCRoute support.
parcellab/monolith/README.md	Documents GRPCRoute support under the Envoy resources section.
parcellab/monolith/templates/grpcroutes.yaml	Wires the new shared GRPCRoute helper into the monolith chart.
parcellab/monolith/values.yaml	Adds envoy.grpcRoutes defaults/examples and updates ReferenceGrant defaults for GRPCRoute.