refactor: remove dead code, hollow stubs, and orphaned modules

Backend — delete 6 orphaned schema sub-modules never imported by any route:
  compliance/schemas/{ai_system,bsi,dashboard,isms_governance,report,service_module}.py
  All symbols were only accessible through the monolithic schemas.py barrel;
  the split files were never wired up and created misleading import paths.

Frontend — delete 2 hollow "future implementation" stub pages:
  app/sdk/agents/sessions/page.tsx
  app/sdk/agents/statistics/page.tsx
  Both showed a static placeholder with no API calls or real functionality.

Frontend — delete dead demo seed/clear API routes:
  app/api/sdk/v1/demo/{seed,clear}/route.ts
  Used a global in-memory store never connected to PostgreSQL.
  The actual demo seeding (lib/sdk/demo-data/) goes through the real
  state API (apiClient.saveState/deleteState), not these routes.

Frontend — remove unimplemented PDF export alert from retention page:
  app/sdk/einwilligungen/retention/page.tsx
  Removed the PDF button and alert('PDF-Export wird noch implementiert.')
  stub. CSV and JSON export remain fully functional.

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

admin-compliance/app/api/sdk/v1/demo/clear/route.ts

@@ -1,52 +0,0 @@
-/**
- * Demo Data Clear API Endpoint
- *
- * Clears demo data from the storage (same mechanism as real customer data).
- */
-
-import { NextRequest, NextResponse } from 'next/server'
-
-// Shared store reference (same as seed endpoint)
-declare global {
-  // eslint-disable-next-line no-var
-  var demoStateStore: Map<string, { state: unknown; version: number; updatedAt: Date }> | undefined
-}
-
-if (!global.demoStateStore) {
-  global.demoStateStore = new Map()
-}
-
-const stateStore = global.demoStateStore
-
-export async function DELETE(request: NextRequest) {
-  try {
-    const body = await request.json()
-    const { tenantId = 'demo-tenant' } = body
-
-    const existed = stateStore.has(tenantId)
-    stateStore.delete(tenantId)
-
-    return NextResponse.json({
-      success: true,
-      message: existed
-        ? `Demo data cleared for tenant ${tenantId}`
-        : `No data found for tenant ${tenantId}`,
-      tenantId,
-      existed,
-    })
-  } catch (error) {
-    console.error('Failed to clear demo data:', error)
-    return NextResponse.json(
-      {
-        success: false,
-        error: error instanceof Error ? error.message : 'Unknown error',
-      },
-      { status: 500 }
-    )
-  }
-}
-
-export async function POST(request: NextRequest) {
-  // Also support POST for clearing (for clients that don't support DELETE)
-  return DELETE(request)
-}

admin-compliance/app/api/sdk/v1/demo/seed/route.ts

@@ -1,77 +0,0 @@
-/**
- * Demo Data Seed API Endpoint
- *
- * This endpoint seeds demo data via the same storage mechanism as real customer data.
- * Demo data is NOT hardcoded - it goes through the normal API/database path.
- */
-
-import { NextRequest, NextResponse } from 'next/server'
-import { generateDemoState } from '@/lib/sdk/demo-data'
-
-// In-memory store (same as state endpoint - will be replaced with PostgreSQL)
-declare global {
-  // eslint-disable-next-line no-var
-  var demoStateStore: Map<string, { state: unknown; version: number; updatedAt: Date }> | undefined
-}
-
-if (!global.demoStateStore) {
-  global.demoStateStore = new Map()
-}
-
-const stateStore = global.demoStateStore
-
-export async function POST(request: NextRequest) {
-  try {
-    const body = await request.json()
-    const { tenantId = 'demo-tenant', userId = 'demo-user' } = body
-
-    // Generate demo state using the seed data templates
-    const demoState = generateDemoState(tenantId, userId)
-
-    // Store via the same mechanism as real data
-    const storedState = {
-      state: demoState,
-      version: 1,
-      updatedAt: new Date(),
-    }
-
-    stateStore.set(tenantId, storedState)
-
-    return NextResponse.json({
-      success: true,
-      message: `Demo data seeded for tenant ${tenantId}`,
-      tenantId,
-      version: 1,
-    })
-  } catch (error) {
-    console.error('Failed to seed demo data:', error)
-    return NextResponse.json(
-      {
-        success: false,
-        error: error instanceof Error ? error.message : 'Unknown error',
-      },
-      { status: 500 }
-    )
-  }
-}
-
-export async function GET(request: NextRequest) {
-  const { searchParams } = new URL(request.url)
-  const tenantId = searchParams.get('tenantId') || 'demo-tenant'
-
-  const stored = stateStore.get(tenantId)
-
-  if (!stored) {
-    return NextResponse.json({
-      hasData: false,
-      tenantId,
-    })
-  }
-
-  return NextResponse.json({
-    hasData: true,
-    tenantId,
-    version: stored.version,
-    updatedAt: stored.updatedAt,
-  })
-}