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/api-keys/dto/create-api-key.dto.ts

@@ -0,0 +1,42 @@
+import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
+import {
+  ArrayMinSize,
+  ArrayUnique,
+  IsArray,
+  IsIn,
+  IsInt,
+  IsOptional,
+  IsString,
+  Max,
+  MaxLength,
+  Min,
+  MinLength,
+} from 'class-validator';
+import { API_KEY_SCOPES } from '../api-key-scopes';
+
+export class CreateApiKeyDto {
+  @ApiProperty({
+    description: 'Wofür der Schlüssel ist, z. B. "Wabenhain-Shop"',
+  })
+  @IsString()
+  @MinLength(1)
+  @MaxLength(80)
+  name!: string;
+
+  @ApiProperty({ enum: API_KEY_SCOPES, isArray: true })
+  @IsArray()
+  @ArrayMinSize(1)
+  @ArrayUnique()
+  @IsIn(API_KEY_SCOPES, { each: true })
+  scopes!: string[];
+
+  @ApiPropertyOptional({
+    description:
+      'Gültigkeit in Tagen; ohne Angabe gilt der Schlüssel bis zum Widerruf',
+  })
+  @IsOptional()
+  @IsInt()
+  @Min(1)
+  @Max(730)
+  expiresInDays?: number;
+}