feat(documents): migrate storage to filesystem, add server-side pagination

- Replace Base64 data URIs with file-based storage served via dedicated endpoints
- Add DocumentPreviewModal navigation, DocumentThumbnail fileUrl support
- Refactor documents page with server-side pagination, search, sort and filters
- Update all components to use fileUrl/downloadUrl instead of raw path
- Add pagination composable support (total, page, itemsPerPage, attachmentFilter)

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

app/components/DocumentThumbnail.vue

@@ -40,6 +40,8 @@ type GenericDocument = {
   filename?: string | null;
   mimeType?: string | null;
   path?: string | null;
+  fileUrl?: string | null;
+  downloadUrl?: string | null;
   size?: number | null;
 };
 
@@ -52,7 +54,7 @@ const normalizedDocument = computed(() => props.document ?? null);
 
 const canRenderImage = computed(() => {
   const doc = normalizedDocument.value;
-  return !!(doc && isImageDocument(doc) && doc.path);
+  return !!(doc && isImageDocument(doc) && (doc.fileUrl || doc.path));
 });
 
 const canRenderPdf = computed(() => {
@@ -73,13 +75,14 @@ const appendPdfViewerParams = (src: string) => {
 
 const previewSrc = computed(() => {
   const doc = normalizedDocument.value;
-  if (!doc || !doc.path) {
+  const url = doc?.fileUrl || doc?.path;
+  if (!doc || !url) {
     return '';
   }
   if (isPdfDocument(doc)) {
-    return appendPdfViewerParams(doc.path);
+    return appendPdfViewerParams(url);
   }
-  return doc.path;
+  return url;
 });
 
 const thumbnailClass = computed(() => (canRenderImage.value || canRenderPdf.value ? 'h-20 w-16' : 'h-16 w-16'));