fix(milestones): enforce valid status transitions with state machine …

[AnoukRImola]

fix(milestones): enforce valid status transitions with state machine and logging

Closes: #121

Summary

• Added a pure milestone state machine (milestoneTransitions.ts) with
  chain-aligned statuses: pending | in_progress | completed | failed
• Rewrote milestones.ts service to be repository-backed (async, DB-driven)
  instead of in-memory
• Extended milestoneRepository.ts with getById and allCompletedByVault
  methods
• Added PATCH /:id/transition endpoint with RBAC (VERIFIER/ADMIN for
  terminal states)
• Kept PATCH /:id/verify as legacy alias that transitions to completed
• Updated vaultTransitions.ts to use allMilestonesCompleted() (async,
  DB-backed)
• Removed conflicting migration 20260226014238_create_milestones_table.cjs
• Added observable logging on transitions (success, rejection, auto-complete)
  without leaking PII
• Fixed pre-existing issues in vaults.ts, vault.service.ts, and knex.ts
  (dead code, duplicate exports, bad merge artifacts)

Valid transitions

pending → [in_progress]
in_progress → [completed, failed, pending]
completed → [] (terminal)
failed → [] (terminal)

Files changed

File	Action
src/types/milestone.ts	Rewritten — chain-aligned types,
VALID_TRANSITIONS, TERMINAL_STATUSES
src/services/milestoneTransitions.ts	New — pure state machine
src/repositories/milestoneRepository.ts	Extended — getById,
allCompletedByVault
src/services/milestones.ts	Rewritten — repository-backed CRUD +
transitions
src/routes/milestones.ts	Updated — async handlers, transition endpoint,
logging
src/services/vaultTransitions.ts	Updated — async, uses
allMilestonesCompleted()
src/services/expirationScheduler.ts	Updated — async callback
src/routes/vaults.ts	Fixed — dead code, duplicate routes, duplicate
imports
src/services/vault.service.ts	Fixed — removed duplicate class from bad
merge
src/db/knex.ts	Fixed — removed duplicate export block
src/tests/milestoneTransitions.test.ts	New — 13 unit tests
src/tests/vaultTransitions.test.ts	Updated — mocked milestones service
db/migrations/20260226014238_create_milestones_table.cjs	Deleted —
conflicted with chain-aligned migration

Test plan

• milestoneTransitions.test.ts — 13/13 passing (valid, invalid,
  terminal, unknown)
• vaultTransitions.test.ts — 18/18 unit tests passing (state machine +
  helpers)
• 14 HTTP integration tests have pre-existing failures (ESM + session.ts
  db mock issue, unrelated to this PR)

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[1nonlypiece]

Please resolve the conflicts

[AnoukRImola]

Please resolve the conflicts

Ready