feat: Add SDK Protection Middleware against systematic enumeration

Implements anomaly-score-based middleware to protect SDK/Compliance
endpoints from systematic data harvesting. Includes 5 detection
mechanisms (diversity, burst, sequential enumeration, unusual hours,
multi-tenant), multi-window quota system, progressive throttling,
HMAC watermarking, and graceful Valkey fallback.

- backend/middleware/sdk_protection.py: Core middleware (~750 lines)
- Admin API endpoints for score management and tier configuration
- 14 new tests (all passing)
- MkDocs documentation with clear explanations
- Screen flow and middleware dashboard updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

website/app/admin/middleware/page.tsx

@@ -85,6 +85,11 @@ const MIDDLEWARE_INFO: Record<string, { name: string; description: string; icon:
     description: 'Validates request body size and content types',
     icon: '🚧',
   },
+  sdk_protection: {
+    name: 'SDK Protection',
+    description: 'Protects SDK endpoints from systematic enumeration (Anomaly-Score, Diversity, Burst, Sequential Detection)',
+    icon: '🔰',
+  },
 }
 
 export default function MiddlewarePage() {

website/app/admin/screen-flow/page.tsx

@@ -120,6 +120,7 @@ const ADMIN_SCREENS: ScreenDefinition[] = [
   { id: 'admin-onboarding', name: 'Onboarding', description: 'Lern-Wizards für alle Module', category: 'overview', icon: '📖', url: '/admin/onboarding' },
   { id: 'admin-gpu', name: 'GPU Infrastruktur', description: 'vast.ai GPU Management', category: 'infrastructure', icon: '🖥️', url: '/admin/gpu' },
   { id: 'admin-middleware', name: 'Middleware', description: 'Middleware Stack & Test', category: 'infrastructure', icon: '🔧', url: '/admin/middleware' },
+  { id: 'admin-sdk-protection', name: 'SDK Protection', description: 'Anomaly-Score & Enumeration-Schutz', category: 'security', icon: '🔰', url: '/admin/middleware' },
   { id: 'admin-mac-mini', name: 'Mac Mini', description: 'Headless Mac Mini Control', category: 'infrastructure', icon: '🍎', url: '/admin/mac-mini' },
   { id: 'admin-consent', name: 'Consent Verwaltung', description: 'Rechtliche Dokumente', category: 'compliance', icon: '📄', url: '/admin/consent' },
   { id: 'admin-dsr', name: 'Datenschutzanfragen', description: 'DSGVO Art. 15-21', category: 'compliance', icon: '🔒', url: '/admin/dsr' },
@@ -169,7 +170,9 @@ const ADMIN_CONNECTIONS: ConnectionDef[] = [
   { source: 'admin-communication', target: 'admin-alerts' },
   { source: 'admin-alerts', target: 'admin-mail' },
   { source: 'admin-gpu', target: 'admin-middleware' },
+  { source: 'admin-middleware', target: 'admin-sdk-protection', label: 'SDK Schutz' },
   { source: 'admin-middleware', target: 'admin-mac-mini' },
+  { source: 'admin-sdk-protection', target: 'admin-security', label: 'Anomaly-Scores' },
   { source: 'admin-game', target: 'admin-unity-bridge' },
   { source: 'admin-edu-search', target: 'admin-staff-search' },
   { source: 'admin-staff-search', target: 'admin-uni-crawler' },