KeepKey Vault v1.5.7

What's Changed

• release: v1.5.4 — certified signing and emulator integration by @BitHighlander in #430
• fix(emulator): carry v1.5.4 start flow into master by @BitHighlander in #431
• Release KeepKey Vault v1.5.5 by @BitHighlander in #435
• CI: classify macOS QA Swift helpers as test sources by @BitHighlander in #437
• Sync v1.5.5 master back into develop by @BitHighlander in #439
• fix(vault): require AdvancedMode for transformERC20 by @BitHighlander in #429
• fix(vault): retain 1.5.5 baseline and address QA feedback by @BitHighlander in #440
• fix(bitcoin-only): enforce host boundary on current develop by @BitHighlander in #441

Full Changelog: v1.5.5...v1.5.7