v0.5.0

• feat(broker): least-privilege operator role, fail-closed health test (a5850f6)
• feat(broker): always keep the secret on an ambiguous commit (8bfdc41)
• feat(broker): reject whitespace-only client secrets at registration (0c6d907)
• feat(broker): keep the secret on an ambiguous commit, document recovery (58b155d)
• feat(broker): publish a provider only once its secret exists (7c07ce9)
• feat(broker): lock rotations per provider, fail closed on blank secrets (5b86031)
• feat(broker): clear a legacy column secret on external-backend delete (08500e2)
• feat(broker): safer registration rollback, idempotent version retirement (bcd0df5)
• feat(broker): refuse NULL secrets in internal mode, wire Compose, bound reads (47d707b)
• feat(broker): bound probe cleanup, type validation errors, atomic delete (29dd5e5)
• feat(broker): probe with a fresh key through Set, Get and Delete (0b6b118)
• feat(broker): surface backend outages honestly and probe create at startup (f68c74c)
• feat(broker): reject empty secrets, keep vault wrappers, bound the probe (01414fb)
• feat(broker): keep legacy secrets on PUT, guard PATCH, build with Go 1.26 (d856f81)
• feat(broker): close the remaining secret backend review notes (cda9929)
• feat(broker): harden the secret backend on review (86a40d1)
• chore(release): 0.5.0 (25d6a02)
• feat(broker): store provider client secrets in GCP Secret Manager (f4e0400)
• refactor(broker): move token encryption to pkg/vault/tokens (064866a)