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/workflows/check-runtime-migration.yml

@@ -85,6 +85,7 @@ jobs:
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Download CLI
+        # NOTE: try-runtime-cli is an upstream shared tool from paritytech/try-runtime-cli
         run: |
           curl -sL https://github.com/paritytech/try-runtime-cli/releases/download/v0.8.0/try-runtime-x86_64-unknown-linux-musl -o try-runtime
           chmod +x ./try-runtime