feat: revocable read-only API keys for machine access

Integrations such as the Wabenhain shop sync no longer need a service
account with a password (and without MFA). An admin creates a key under
Verwaltung > Automatisierung > API-Schlüssel.

- Key format ack_<8>_<43>; only its SHA-256 hash is stored, the key is
  shown exactly once. Optional expiry, "last used" timestamp, revocation
  takes effect immediately; create/revoke are audit-logged without the key.
- A key is not a user: JwtAuthGuard sets request.apiKey, PermissionsGuard
  admits it only to routes whose permission is among its scopes and never
  to user-only routes. Scopes come from a short allowlist (shop-sync:read).
- Managing keys requires the new permission api-keys:manage.
- Keys are excluded from backups on purpose; a restore means issuing a new
  key.

Additive migration (new table).

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Backend/src/auth/guards/jwt-auth.guard.ts

@@ -8,9 +8,16 @@ import { AuthGuard } from '@nestjs/passport';
 import { IS_PUBLIC_KEY } from '../decorators/public.decorator';
 import { PermissionResolverService } from '../permissions/permission-resolver.service';
 import { AuthenticatedUser } from '../types/authenticated-user';
+import {
+  ApiKeyPrincipal,
+  ApiKeysService,
+  extractApiKeyToken,
+} from '../../api-keys/api-keys.service';
 
 interface RequestWithUser {
+  headers: { authorization?: string };
   user?: AuthenticatedUser;
+  apiKey?: ApiKeyPrincipal;
 }
 
 /**
@@ -28,6 +35,7 @@ export class JwtAuthGuard extends AuthGuard('jwt') {
   constructor(
     private readonly reflector: Reflector,
     private readonly permissionResolver: PermissionResolverService,
+    private readonly apiKeys: ApiKeysService,
   ) {
     super();
   }
@@ -40,11 +48,25 @@ export class JwtAuthGuard extends AuthGuard('jwt') {
     if (isPublic) {
       return true;
     }
+    const request = context.switchToHttp().getRequest<RequestWithUser>();
+
+    // An API key ("Bearer ack_…") authenticates a machine, not a user: no
+    // request.user is set, so it can never pass a user-only route, and
+    // PermissionsGuard checks its scopes instead of a role.
+    const apiKeyToken = extractApiKeyToken(request.headers.authorization);
+    if (apiKeyToken !== null) {
+      const principal = await this.apiKeys.authenticate(apiKeyToken);
+      if (!principal) {
+        throw new UnauthorizedException();
+      }
+      request.apiKey = principal;
+      return true;
+    }
+
     const authenticated = (await super.canActivate(context)) as boolean;
     if (!authenticated) {
       return false;
     }
-    const request = context.switchToHttp().getRequest<RequestWithUser>();
     const user = request.user;
     if (
       !user ||