feat: add document deletion endpoint and UI button (AIIA-70)

Add DELETE /api/documents/:id endpoint that removes the DB record,
cleans up the stored file from disk, and logs an audit event. Add a
"Loeschen" button to the DokumentUpload component with confirmation
dialog.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/app/api/documents/[id]/route.ts

@@ -1,7 +1,9 @@
-// GET /api/documents/:id — get document status and metadata (used for polling)
+// GET    /api/documents/:id — get document status and metadata (used for polling)
+// DELETE /api/documents/:id — delete a document and its stored file
 
 import { type NextRequest } from 'next/server';
-import { getDocument } from '@/lib/documents';
+import { getDocument, deleteDocument } from '@/lib/documents';
+import { logAuditEvent } from '@/lib/auth/audit';
 import { requirePermission } from '@/lib/auth/rbac';
 
 export async function GET(
@@ -32,3 +34,31 @@ export async function GET(
     updatedAt: doc.updatedAt,
   });
 }
+
+export async function DELETE(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  const auth = await requirePermission('cases:edit');
+  if ('response' in auth) return auth.response;
+  const { ctx } = auth;
+
+  const { id } = await params;
+
+  const deleted = await deleteDocument(ctx.tenantId, id);
+
+  if (!deleted) {
+    return Response.json(
+      { error: 'Dokument nicht gefunden.' },
+      { status: 404 },
+    );
+  }
+
+  const ip =
+    request.headers.get('x-forwarded-for')?.split(',')[0]?.trim() ??
+    request.headers.get('x-real-ip') ??
+    undefined;
+  await logAuditEvent(ctx, 'delete', 'document', id, { filename: deleted.filename }, ip);
+
+  return Response.json({ deleted: true });
+}

src/components/documents/dokument-upload.tsx

@@ -121,6 +121,7 @@ export default function DokumentUpload({
   label = 'Dokument hochladen',
 }: DokumentUploadProps) {
   const [uploading, setUploading] = useState(false);
+  const [deleting, setDeleting] = useState<string | null>(null);
   const [error, setError] = useState('');
   const [success, setSuccess] = useState('');
   const [documents, setDocuments] = useState<DocumentItem[]>([]);
@@ -204,6 +205,28 @@ export default function DokumentUpload({
     }
   }
 
+  async function handleDelete(docId: string, filename: string) {
+    if (!confirm(`"${filename}" wirklich loeschen?`)) return;
+
+    setError('');
+    setSuccess('');
+    setDeleting(docId);
+
+    try {
+      const res = await fetch(`/api/documents/${docId}`, { method: 'DELETE' });
+      if (!res.ok) {
+        const data = await res.json();
+        throw new Error(data.error || 'Loeschen fehlgeschlagen');
+      }
+      setSuccess(`"${filename}" wurde geloescht.`);
+      fetchDocuments();
+    } catch (err) {
+      setError(err instanceof Error ? err.message : 'Ein Fehler ist aufgetreten');
+    } finally {
+      setDeleting(null);
+    }
+  }
+
   function handleSubmit(e: React.FormEvent) {
     e.preventDefault();
     const file = fileRef.current?.files?.[0];
@@ -305,6 +328,15 @@ export default function DokumentUpload({
                   >
                     {STATUS_LABELS[doc.status] ?? doc.status}
                   </span>
+                  <button
+                    type="button"
+                    onClick={() => handleDelete(doc.id, doc.filename)}
+                    disabled={deleting === doc.id}
+                    className="ml-2 text-xs text-danger hover:text-danger/80 transition-colors disabled:opacity-50 shrink-0"
+                    title="Dokument loeschen"
+                  >
+                    {deleting === doc.id ? '...' : 'Loeschen'}
+                  </button>
                 </div>
 
                 {/* Show progress for non-extracted documents or if debug is on */}

src/lib/documents/index.ts

@@ -258,3 +258,26 @@ export async function getDocument(tenantId: string, documentId: string) {
     return doc ?? null;
   });
 }
+
+/**
+ * Delete a document by ID. Removes the DB record and the stored file from disk.
+ * Returns the deleted document row, or null if not found.
+ */
+export async function deleteDocument(tenantId: string, documentId: string) {
+  const deleted = await withTenantDb(tenantId, async (tdb) => {
+    const [row] = await tdb
+      .delete(documents)
+      .where(eq(documents.id, documentId))
+      .returning();
+    return row ?? null;
+  });
+
+  if (deleted?.storagePath) {
+    const fs = await import('node:fs/promises');
+    await fs.unlink(deleted.storagePath).catch(() => {
+      // File may already be removed — ignore cleanup errors
+    });
+  }
+
+  return deleted;
+}