feat: Add Document Crawler frontend page and API proxy (Phase 1.4)

4-tab page (Quellen, Crawl-Jobs, Dokumente, Onboarding-Report) and
catch-all API proxy route to document-crawler service on port 8098.

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

admin-v2/app/api/sdk/v1/crawler/[[...path]]/route.ts

@@ -0,0 +1,114 @@
+/**
+ * Document Crawler API Proxy - Catch-all route
+ * Proxies all /api/sdk/v1/crawler/* requests to document-crawler service (port 8098)
+ */
+
+import { NextRequest, NextResponse } from 'next/server'
+
+const CRAWLER_BACKEND_URL = process.env.CRAWLER_API_URL || 'http://document-crawler:8098'
+
+async function proxyRequest(
+  request: NextRequest,
+  pathSegments: string[] | undefined,
+  method: string
+) {
+  const pathStr = pathSegments?.join('/') || ''
+  const searchParams = request.nextUrl.searchParams.toString()
+  const basePath = `${CRAWLER_BACKEND_URL}/api/v1/crawler`
+  const url = pathStr
+    ? `${basePath}/${pathStr}${searchParams ? `?${searchParams}` : ''}`
+    : `${basePath}${searchParams ? `?${searchParams}` : ''}`
+
+  try {
+    const headers: HeadersInit = {
+      'Content-Type': 'application/json',
+    }
+
+    // Forward all relevant headers
+    const headerNames = ['authorization', 'x-tenant-id', 'x-user-id', 'x-namespace-id', 'x-tenant-slug']
+    for (const name of headerNames) {
+      const value = request.headers.get(name)
+      if (value) {
+        headers[name] = value
+      }
+    }
+
+    const fetchOptions: RequestInit = {
+      method,
+      headers,
+      signal: AbortSignal.timeout(30000),
+    }
+
+    // Forward body for non-GET requests
+    if (method !== 'GET' && method !== 'DELETE') {
+      try {
+        const body = await request.json()
+        fetchOptions.body = JSON.stringify(body)
+      } catch {
+        // No body or non-JSON body
+      }
+    }
+
+    const response = await fetch(url, fetchOptions)
+
+    if (!response.ok) {
+      const errorText = await response.text()
+      let errorJson
+      try {
+        errorJson = JSON.parse(errorText)
+      } catch {
+        errorJson = { error: errorText }
+      }
+      return NextResponse.json(
+        { error: `Backend Error: ${response.status}`, ...errorJson },
+        { status: response.status }
+      )
+    }
+
+    // Handle 204 No Content
+    if (response.status === 204) {
+      return new NextResponse(null, { status: 204 })
+    }
+
+    const data = await response.json()
+    return NextResponse.json(data)
+  } catch (error) {
+    console.error('Document Crawler API proxy error:', error)
+    return NextResponse.json(
+      { error: 'Verbindung zum Document Crawler Backend fehlgeschlagen' },
+      { status: 503 }
+    )
+  }
+}
+
+export async function GET(
+  request: NextRequest,
+  { params }: { params: Promise<{ path?: string[] }> }
+) {
+  const { path } = await params
+  return proxyRequest(request, path, 'GET')
+}
+
+export async function POST(
+  request: NextRequest,
+  { params }: { params: Promise<{ path?: string[] }> }
+) {
+  const { path } = await params
+  return proxyRequest(request, path, 'POST')
+}
+
+export async function PUT(
+  request: NextRequest,
+  { params }: { params: Promise<{ path?: string[] }> }
+) {
+  const { path } = await params
+  return proxyRequest(request, path, 'PUT')
+}
+
+export async function DELETE(
+  request: NextRequest,
+  { params }: { params: Promise<{ path?: string[] }> }
+) {
+  const { path } = await params
+  return proxyRequest(request, path, 'DELETE')
+}