feat: /v1/role list, get, create, update and delete. Reassign members on delete. Write-time validation (ValidateGrants, duplicates, typed keys against real content types). Name uniqueness (role_name_taken), role_locked, role_has_members, role_conflict on version mismatch. No-escalation: nobody grants a permission they don't hold, and roles.edit_owner_only guards the Owner role. Activity events for role changes. Typed-key exposure in /auth/me. Cleanup of typed rows when a content type is deleted. | Backend only. Will carry the deferred ListGrants decision.

api/pkg/apperr/messages.go

@@ -100,3 +100,21 @@ const InvalidFieldErrorMessage = "invalid_field"
 const SchemaIncompatibleErrorMessage = "schema_incompatible"
 const EntryNotFoundErrorMessage = "entry_not_found"
 const InvalidEntryErrorMessage = "invalid_entry"
+
+const RoleNotFoundErrorMessage = "role_not_found"
+const RoleLockedErrorMessage = "role_locked"
+const RoleBuiltInErrorMessage = "role_built_in"
+const BuiltInNameErrorMessage = "built_in_name"
+const NotBuiltInErrorMessage = "not_built_in"
+const OwnRoleErrorMessage = "own_role"
+const EscalationErrorMessage = "escalation"
+const EscalationHeader = "X-Escalation-Key"
+const RoleNameTakenErrorMessage = "role_name_taken"
+const RoleConflictErrorMessage = "role_conflict"
+const RoleHasMembersErrorMessage = "role_has_members"
+const InvalidRoleNameErrorMessage = "invalid_role_name"
+const UnknownPermissionErrorMessage = "unknown_permission"
+const InvalidScopeErrorMessage = "invalid_scope"
+const OwnerOnlyPermissionErrorMessage = "owner_only_permission"
+const DuplicatePermissionErrorMessage = "duplicate_permission"
+const UnknownContentTypeErrorMessage = "unknown_content_type"