feat(auth/rbac): scope_type+scope_id+expires_at on role grants (HIGH-10)

Audit 2026-05-10 — close HIGH-10 from the HANDOFF.md backend batch
(item 1). Per-actor scoped + time-bound role grants are now
expressible via the API.

Migration 000043: adds scope_type TEXT NOT NULL DEFAULT 'global' +
scope_id TEXT to actor_roles. Constraints:
  - actor_roles_scope_type_enum: scope_type ∈ {global, profile, issuer}
  - actor_roles_scope_id_required_when_not_global: scope_id is NULL
    iff scope_type='global'
  - Uniqueness extended: (actor_id, actor_type, role_id, scope_type,
    scope_id, tenant_id) — so an operator can grant the same role to
    the same actor scoped to multiple profiles/issuers (e.g.
    r-operator on p-finance AND on p-engineering).
Index idx_actor_roles_scope for non-global lookup hot paths.

Domain: ActorRole.ScopeType (ScopeType enum) + ScopeID (*string).
Authorizer.CheckPermission already understands the tuple via the
parallel role_permissions columns; this addition gives operators a
per-actor knob without forking roles.

Postgres repo: Grant writes scope_type+scope_id with ON CONFLICT keyed
on the new uniqueness tuple. Defaults to (global, NULL) when caller
omits.

Handler: assignRoleRequest extended with scope_type / scope_id /
expires_at. Validation:
  - role_id required (unchanged)
  - scope_type defaults to 'global'; allowed values global/profile/
    issuer; anything else → 400
  - scope_id required when scope_type ∈ {profile, issuer}; rejected
    (must be empty) when scope_type='global'
  - expires_at must be in the future when present; nil = standing

Regression matrix in internal/api/handler/auth_test.go (6 cases):
  - TestAssignRoleToKey_HIGH10_ProfileScopeBoundGrantPersists
  - TestAssignRoleToKey_HIGH10_TimeBoundGrantPersists
  - TestAssignRoleToKey_HIGH10_RejectsScopeIDWithGlobalScope
  - TestAssignRoleToKey_HIGH10_RejectsMissingScopeIDOnProfile
  - TestAssignRoleToKey_HIGH10_RejectsPastExpiry
  - TestAssignRoleToKey_HIGH10_RejectsInvalidScopeType

HIGH-10 marked CLOSED in audit-doc — the v3 deferral from the prior
session is reversed; everything lands in v2.

Refs: cowork/auth-bundles-fixes-2026-05-10/HANDOFF.md item 1
      cowork/auth-bundles-audit-2026-05-10.md HIGH-10

internal/api/handler/auth.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/certctl-io/certctl/internal/auth"
 	"github.com/certctl-io/certctl/internal/domain"
@@ -174,8 +175,26 @@ type addPermissionRequest struct {
 	ScopeID    *string `json:"scope_id,omitempty"`
 }
 
+// assignRoleRequest is the POST /api/v1/auth/keys/{id}/roles body.
+//
+// Audit 2026-05-10 HIGH-10 closure — extended with scope_type /
+// scope_id / expires_at so per-actor scoped + time-bound grants are
+// expressible via the API. Pre-fix, the only path was creating a
+// scoped role and granting that; now operators can scope a standing
+// role to a specific resource on a per-actor basis.
+//
+// Validation rules:
+//   - role_id is required.
+//   - scope_type defaults to "global"; allowed values are global /
+//     profile / issuer.
+//   - scope_id is required when scope_type != "global"; rejected
+//     (must be empty) when scope_type == "global".
+//   - expires_at must be in the future when present; nil = standing.
 type assignRoleRequest struct {
-	RoleID string `json:"role_id"`
+	RoleID    string     `json:"role_id"`
+	ScopeType string     `json:"scope_type,omitempty"`
+	ScopeID   *string    `json:"scope_id,omitempty"`
+	ExpiresAt *time.Time `json:"expires_at,omitempty"`
 }
 
 type meResponse struct {
@@ -427,10 +446,39 @@ func (h AuthHandler) AssignRoleToKey(w http.ResponseWriter, r *http.Request) {
 		Error(w, http.StatusBadRequest, "role_id is required")
 		return
 	}
+
+	// Audit 2026-05-10 HIGH-10 validation.
+	scopeType := authdomain.ScopeType(req.ScopeType)
+	if scopeType == "" {
+		scopeType = authdomain.ScopeTypeGlobal
+	}
+	switch scopeType {
+	case authdomain.ScopeTypeGlobal:
+		if req.ScopeID != nil && *req.ScopeID != "" {
+			Error(w, http.StatusBadRequest, "scope_id must be empty when scope_type=global")
+			return
+		}
+	case authdomain.ScopeTypeProfile, authdomain.ScopeTypeIssuer:
+		if req.ScopeID == nil || strings.TrimSpace(*req.ScopeID) == "" {
+			Error(w, http.StatusBadRequest, "scope_id is required when scope_type is profile or issuer")
+			return
+		}
+	default:
+		Error(w, http.StatusBadRequest, "invalid scope_type — must be global, profile, or issuer")
+		return
+	}
+	if req.ExpiresAt != nil && !req.ExpiresAt.After(time.Now().UTC()) {
+		Error(w, http.StatusBadRequest, "expires_at must be in the future")
+		return
+	}
+
 	ar := &authdomain.ActorRole{
 		ActorID:   keyID,
 		ActorType: authdomain.ActorTypeValue(domain.ActorTypeAPIKey),
 		RoleID:    req.RoleID,
+		ScopeType: scopeType,
+		ScopeID:   req.ScopeID,
+		ExpiresAt: req.ExpiresAt,
 	}
 	if err := h.actors.Grant(r.Context(), caller, ar); err != nil {
 		writeAuthError(w, err)