feat(docs-ui): shared FileIcon + signed-state pill on EntityFolderView rows

- Extract FileIcon mapping to `src/components/files/file-icon.tsx` (single
  source of truth for mime→icon+colour palette; was previously inline in
  FileGrid only).
- EntityFolderView file rows now render the type-specific icon (PDF/red,
  Image/blue, Sheet/green, Video/purple) instead of a generic FileText —
  multi-deal clients become scannable at a glance.
- Add an inline "Signed" pill on rows where signedFromDocumentId is set so
  reps can distinguish a signed-from-workflow copy from a vanilla upload
  without hovering for "View signing details".
- Tighter hover treatment (row picks up a subtle bg on hover) for affordance.
- FileGrid refactored to consume the shared FileIcon so both surfaces stay
  in lockstep on future mime additions.

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

src/components/files/file-grid.tsx

@@ -1,17 +1,10 @@
 'use client';
 
-import {
-  Download,
-  FileText,
-  Film,
-  Image,
-  MoreHorizontal,
-  Pencil,
-  Sheet,
-  Trash2,
-} from 'lucide-react';
+import { Download, FileText, MoreHorizontal, Pencil, Trash2 } from 'lucide-react';
 import { format } from 'date-fns';
 
+import { FileIcon as SharedFileIcon } from './file-icon';
+
 import { Button } from '@/components/ui/button';
 import {
   DropdownMenu,
@@ -56,19 +49,7 @@ function formatBytes(bytes: string | null): string {
 }
 
 function FileIcon({ mimeType }: { mimeType: string | null }) {
-  if (!mimeType) return <FileText className="h-8 w-8 text-muted-foreground" />;
-  // eslint-disable-next-line jsx-a11y/alt-text
-  if (mimeType.startsWith('image/')) return <Image className="h-8 w-8 text-blue-500" />;
-  if (mimeType === 'application/pdf') return <FileText className="h-8 w-8 text-red-500" />;
-  if (
-    mimeType === 'application/vnd.ms-excel' ||
-    mimeType === 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' ||
-    mimeType === 'text/csv'
-  ) {
-    return <Sheet className="h-8 w-8 text-green-600" />;
-  }
-  if (mimeType.startsWith('video/')) return <Film className="h-8 w-8 text-purple-500" />;
-  return <FileText className="h-8 w-8 text-muted-foreground" />;
+  return <SharedFileIcon mimeType={mimeType} className="h-8 w-8" />;
 }
 
 export function FileGrid({