Release Platform v2: signed updater, transactional installer, rollback

[MrPastio]

Что входит

• exact-byte Ed25519 stable manifest и draft-first distribution pipeline
• main-process UpdateService с GitHub primary / Sites mirror, anti-replay и resumable download
• versioned app/runtime/backend layout, migration journal, health acknowledgement и launcher rollback
• manual bootstrap release v0.1.5 и update UI
• отдельный public distribution boundary MrPastio/monarch-releases

Проверки

• clean-public branch: typecheck, desktop smoke, 41/41 focused tests, upload dry-run 0 violations
• internal worktree: 103/103 Vitest files, 830/830 tests sequential
• launcher self-test and isolated installed desktop smoke
• Inno Setup final build: AB2EDFFB8AF121C5F54C557CFF34DAC761BEE76239250750D2AC8A855261C447

Почему draft

• stable spec намеренно available=false
• ещё нужен minimal fine-grained MONARCH_RELEASES_TOKEN
• Sites project id сейчас возвращает project_not_found
• остаются 500 MB geo probe и joint 0.1.5 -> 0.2.0 -> 0.2.1 acceptance

Никакой release или stable manifest этим PR не публикуется.