fix: Route all banner API calls through Next.js proxy (SSL cert fix)

Browser blocks direct calls to backend-compliance:8093 due to
self-signed SSL certificate. All banner API calls now go through
Next.js API proxy at /api/sdk/v1/banner/* which runs server-side.

- New catch-all proxy: /api/sdk/v1/banner/[[...path]]/route.ts
  Maps to backend-compliance:8002/api/compliance/banner/*
- Preview page: uses /api/sdk/v1/banner/ instead of https://macmini:8093
- CMP Dashboard: uses proxy for banner stats + compliance proxy for DSR/einwilligungen
- Fixes: banner not closeable due to API errors, consent not saving

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

admin-compliance/app/api/sdk/v1/banner/[[...path]]/route.ts

@@ -0,0 +1,74 @@
+/**
+ * Banner API Proxy — catch-all route for cookie banner endpoints.
+ *
+ * Maps: /api/sdk/v1/banner/<path> → backend-compliance:8002/api/compliance/banner/<path>
+ *
+ * Solves: Browser cannot call backend-compliance:8093 directly due to
+ * self-signed SSL certificates. This proxy runs server-side where
+ * certificate validation is not an issue.
+ */
+
+import { NextRequest, NextResponse } from 'next/server'
+
+const BACKEND_URL = process.env.BACKEND_URL || 'http://backend-compliance:8002'
+const DEFAULT_TENANT = process.env.DEFAULT_TENANT_ID || '9282a473-5c95-4b3a-bf78-0ecc0ec71d3e'
+
+async function proxyRequest(
+  request: NextRequest,
+  pathSegments: string[] | undefined,
+  method: string,
+) {
+  const pathStr = pathSegments?.join('/') || ''
+  const qs = request.nextUrl.searchParams.toString()
+  const base = `${BACKEND_URL}/api/compliance/banner`
+  const url = pathStr
+    ? `${base}/${pathStr}${qs ? `?${qs}` : ''}`
+    : `${base}${qs ? `?${qs}` : ''}`
+
+  try {
+    const headers: HeadersInit = {
+      'X-Tenant-ID': request.headers.get('x-tenant-id') || DEFAULT_TENANT,
+    }
+    const ct = request.headers.get('Content-Type')
+    if (ct) headers['Content-Type'] = ct
+
+    const opts: RequestInit = { method, headers, signal: AbortSignal.timeout(30000) }
+
+    if (method === 'POST' || method === 'PUT') {
+      const body = await request.text()
+      if (body) opts.body = body
+    }
+
+    const res = await fetch(url, opts)
+    const text = await res.text()
+    let data
+    try { data = JSON.parse(text) } catch { data = { raw: text } }
+
+    if (!res.ok) {
+      return NextResponse.json(
+        { error: `Backend ${res.status}`, ...data },
+        { status: res.status },
+      )
+    }
+    return NextResponse.json(data)
+  } catch (err: any) {
+    console.error('Banner proxy error:', err?.message)
+    return NextResponse.json(
+      { error: 'Backend nicht erreichbar' },
+      { status: 503 },
+    )
+  }
+}
+
+export async function GET(req: NextRequest, { params }: { params: Promise<{ path?: string[] }> }) {
+  return proxyRequest(req, (await params).path, 'GET')
+}
+export async function POST(req: NextRequest, { params }: { params: Promise<{ path?: string[] }> }) {
+  return proxyRequest(req, (await params).path, 'POST')
+}
+export async function PUT(req: NextRequest, { params }: { params: Promise<{ path?: string[] }> }) {
+  return proxyRequest(req, (await params).path, 'PUT')
+}
+export async function DELETE(req: NextRequest, { params }: { params: Promise<{ path?: string[] }> }) {
+  return proxyRequest(req, (await params).path, 'DELETE')
+}