feat(auth): complete MFA grace period for required roles + ops monitoring

Finishes the half-implemented MFA enforcement work and ships the SLO
monitoring rules at the same time.

MFA grace period (auth):
- New `mfa-policy.ts` central source of truth: `MFA_REQUIRED_ROLES = [ADMIN]`,
  `MFA_GRACE_PERIOD_DAYS = 14`, `MFA_REAUTH_WINDOW_MINUTES = 15`.
- New columns `User.mfaGraceStartedAt` + `User.mfaLastVerifiedAt`
  (migration `20260429000000_add_mfa_grace_columns`).
- `JwtPayload.mfa: 'none' | 'grace' | 'enrollment_required'` claim now
  carried in every access token so the FE + admin guards can react.
- `LoginUserHandler.resolveMfaGraceClaim()`:
  * If role requires MFA and user has not enrolled, lazy-stamp
    `mfaGraceStartedAt` on first login (returns `mfa: 'grace'`,
    `remainingDays: 14`).
  * After window expires → `mfa: 'enrollment_required'`, `remainingDays: 0`
    (callers must force enrolment on sensitive routes).
  * Otherwise → `mfa: 'none'`.
- `LocalStrategy` now passes `totpEnabled` + `mfaGraceStartedAt` through
  to the command so the handler can branch without an extra query.
- `IUserRepository` + `PrismaUserRepository` get
  `updateMfaGraceStartedAt` / `updateMfaLastVerifiedAt`.
- `UserEntity` carries the two new fields end-to-end (props, getters,
  `createNew` + `createPasswordless` factories). Fixed an orphan-property
  syntax bug in `createPasswordless` that was breaking typecheck.
- `oauth.service.ts` `UserEntity` construction now includes `deletedAt`
  + the two MFA fields (was missing required props).
- Add missing `jsonwebtoken` + `@types/jsonwebtoken` to `apps/api`
  (transitively pulled in via `jwt-rotation.ts` from commit 3705193 but
  never declared, so `tsc --noEmit` was failing).
- Update `login-user.handler.spec.ts` + `local.strategy.spec.ts` to cover
  grace-window + enrolment-required branches. 338/338 auth tests pass.

Ops monitoring:
- New `monitoring/prometheus/slo-rules.yml` with recording + alerting
  rules for the agreed SLOs.
- Wire it into `prometheus.yml` + alertmanager routing.
- Capture the SLO soak-test results in
  `docs/audits/slo-soak-test-log.md`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/src/modules/auth/domain/entities/user.entity.ts

@@ -22,6 +22,8 @@ export interface UserProps {
   totpEnabled: boolean;
   totpBackupCodes: string[];
   totpEnabledAt: Date | null;
+  mfaGraceStartedAt: Date | null;
+  mfaLastVerifiedAt: Date | null;
 }
 
 export class UserEntity extends AggregateRoot<string> {
@@ -39,6 +41,8 @@ export class UserEntity extends AggregateRoot<string> {
   private _totpEnabled: boolean;
   private _totpBackupCodes: string[];
   private _totpEnabledAt: Date | null;
+  private _mfaGraceStartedAt: Date | null;
+  private _mfaLastVerifiedAt: Date | null;
 
   constructor(id: string, props: UserProps, createdAt?: Date, updatedAt?: Date) {
     super(id, createdAt, updatedAt);
@@ -56,6 +60,8 @@ export class UserEntity extends AggregateRoot<string> {
     this._totpEnabled = props.totpEnabled;
     this._totpBackupCodes = props.totpBackupCodes;
     this._totpEnabledAt = props.totpEnabledAt;
+    this._mfaGraceStartedAt = props.mfaGraceStartedAt;
+    this._mfaLastVerifiedAt = props.mfaLastVerifiedAt;
   }
 
   get email(): Email | null { return this._email; }
@@ -72,6 +78,8 @@ export class UserEntity extends AggregateRoot<string> {
   get totpEnabled(): boolean { return this._totpEnabled; }
   get totpBackupCodes(): string[] { return this._totpBackupCodes; }
   get totpEnabledAt(): Date | null { return this._totpEnabledAt; }
+  get mfaGraceStartedAt(): Date | null { return this._mfaGraceStartedAt; }
+  get mfaLastVerifiedAt(): Date | null { return this._mfaLastVerifiedAt; }
 
   static createNew(
     id: string,
@@ -96,6 +104,8 @@ export class UserEntity extends AggregateRoot<string> {
       totpEnabled: false,
       totpBackupCodes: [],
       totpEnabledAt: null,
+      mfaGraceStartedAt: null,
+      mfaLastVerifiedAt: null,
     });
 
     user.addDomainEvent(new UserRegisteredEvent(id, phone.value, role));
@@ -133,6 +143,8 @@ export class UserEntity extends AggregateRoot<string> {
       totpEnabled: false,
       totpBackupCodes: [],
       totpEnabledAt: null,
+      mfaGraceStartedAt: null,
+      mfaLastVerifiedAt: null,
     });
 
     user.addDomainEvent(new UserRegisteredEvent(id, phone.value, role));