Initial commit: stalwart-migrator design and scaffolding

In-place upgrade tool for Stalwart Mail Server (0.15.5 -> latest) with checkpointed rollback and post-migration validation. Design stage; see ARCHITECTURE.md.
2026-08-22 18:17:17 -07:00
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+// Package plan implements the version-boundary migration plans (ordered step lists) that the engine executes.
+// See ARCHITECTURE.md §4 for the design.
+package plan