refactor(ci): decouple from upstream Parity infrastructure

Replace Parity-specific infrastructure dependencies with Pezkuwi's own:
- S3 release uploads → GitHub Releases (gh CLI)
- parity-zombienet runner labels → pezkuwi-runner
- Grafana/Loki log URLs → disabled (use GH artifacts)
- Matrix notifications → disabled (pending Pezkuwi Matrix)
- paritytech issue links → pezkuwi tracking issues
- paritytech Docker image refs → pezkuwi-sdk-frame in cmd.py
- Add mirror-ci-image.yml workflow for GHCR image mirroring
- Document upstream shared tools (resolc, try-runtime, evm-test-suite)

.github/actions/zombienet-sdk/action.yml

@@ -95,7 +95,7 @@ runs:
         else
           export RUN_IN_CI=1
           # no need to check other runner variables. for k8s they shall store the same value
-          if [[ $ZOMBIENET_SDK_DEFAULT_RUNNER == "parity-zombienet" ]]; then
+          if [[ $ZOMBIENET_SDK_DEFAULT_RUNNER == "pezkuwi-runner" ]]; then
             export ZOMBIE_K8S_CI_NAMESPACE=$(cat /data/namespace)
           fi
         fi

.github/actions/zombienet/action.yml

@@ -93,7 +93,7 @@ runs:
             "$TEST_DEFINITION"
         else
           # no need to check other runner variables. for k8s they shall store the same value
-          if [[ $ZOMBIENET_DEFAULT_RUNNER == "parity-zombienet" ]]; then
+          if [[ $ZOMBIENET_DEFAULT_RUNNER == "pezkuwi-runner" ]]; then
             export ZOMBIE_K8S_CI_NAMESPACE=$(cat /data/namespace)
           fi