feat: add e2e test for d8 mirror

[timmilesdw]

Add E2E tests for d8 mirror commands

Summary

Added comprehensive end-to-end tests for d8 mirror pull and d8 mirror push commands with deep registry comparison.

Changes

• New E2E test suite (testing/e2e/mirror/):

  • Full mirror cycle test: pull - push - deep comparison
  • Registry comparator with manifest, config, and layer-level verification
  • Detailed reports

• Taskfile integration:

  • task test:e2e:mirror — run E2E tests
  • task test:e2e:mirror:logs:clean — cleanup test logs

Test Artifacts

Tests produce detailed artifacts in testing/e2e/.logs/<test>-<timestamp>/:

File	Description
test.log	Full command output from pull/push operations
report.txt	Test execution summary with timing and stats
comparison.txt	Detailed registry comparison with per-repo breakdown

These artifacts help debug failures and verify that registries are byte-for-byte identical.

Usage

# Using environment variables
E2E_SOURCE_REGISTRY=localhost:443/deckhouse \
E2E_SOURCE_USER=admin \
E2E_SOURCE_PASSWORD=admin \
E2E_TLS_SKIP_VERIFY=true \
task test:e2e:mirror

# Using command-line flags
task test:e2e:mirror -- -source-registry=... -source-user=... -tls-skip-verify