chore(documents): remove legacy /documents/files route + folder tree

The /documents/files page rendered a storagePath-prefix folder tree
disconnected from document_folders. Replaced by the unified hub
(Task 15). 301 redirect catches stray bookmarks. file-browser-store
repurposed to hold the document_folders.id selection.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

next.config.ts

@@ -72,6 +72,20 @@ const nextConfig: NextConfig = {
     // process.cwd() requires the file to be traced explicitly.
     '/api/v1/document-templates/**': ['./assets/eoi-template.pdf'],
   },
+  async redirects() {
+    return [
+      {
+        source: '/:portSlug/documents/files',
+        destination: '/:portSlug/documents',
+        permanent: true,
+      },
+      {
+        source: '/:portSlug/documents/files/:path*',
+        destination: '/:portSlug/documents',
+        permanent: true,
+      },
+    ];
+  },
   async headers() {
     return [
       {