Fixes Tachyon startup abort when migrated config has no dns_server or
bootstrap_dns_server (forkop/podkop did not require these fields).
Changes:
- migration.uc: add ensure_dns_server_defaults migration that injects
77.88.8.8 as fallback when either dns list is empty
- default config: pre-mark orphan_section_interface_cleanup and
ensure_dns_server_defaults as applied so fresh installs skip them
- tests/config_migration.sh: regression tests for both missing-DNS cases
and stable named-marker assertion for the new migration
- tests/package_contract.sh: enforce that default config ships both new
migration IDs in applied_migrations
- tests/docker_e2e_test.sh: also install luci-app-tachyon and verify
menu.d + acl.d files are present after install (LuCI menu bug class)
Dushnilin
b82a151c87