feat: granular file access audit logging (viewed/opened/downloaded)

Replace single FILE_DOWNLOADED action with three granular actions:
- FILE_VIEWED: inline preview loaded in the UI
- FILE_OPENED: file opened in a new browser tab
- FILE_DOWNLOADED: explicit download button clicked

Add 'purpose' field to getDownloadUrl input (preview/open/download).
All client callers updated to pass the appropriate purpose.
Audit page updated with new filter options and color mappings.

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

src/app/(admin)/admin/audit/page.tsx

@@ -77,6 +77,8 @@ const ACTION_TYPES = [
   'ROUND_ARCHIVED',
   'UPLOAD_FILE',
   'DELETE_FILE',
+  'FILE_VIEWED',
+  'FILE_OPENED',
   'FILE_DOWNLOADED',
   'BULK_CREATE',
   'BULK_UPDATE_STATUS',
@@ -171,6 +173,8 @@ const actionColors: Record<string, 'default' | 'destructive' | 'secondary' | 'ou
   ROUND_ACTIVATED: 'default',
   ROUND_CLOSED: 'secondary',
   ROUND_ARCHIVED: 'secondary',
+  FILE_VIEWED: 'outline',
+  FILE_OPENED: 'outline',
   FILE_DOWNLOADED: 'outline',
   ROLE_CHANGED: 'secondary',
   PASSWORD_SET: 'outline',

src/app/(admin)/admin/projects/bulk-upload/page.tsx

@@ -146,7 +146,7 @@ export default function BulkUploadPage() {
   const handleViewFile = useCallback(
     async (bucket: string, objectKey: string) => {
       try {
-        const { url } = await utils.file.getDownloadUrl.fetch({ bucket, objectKey })
+        const { url } = await utils.file.getDownloadUrl.fetch({ bucket, objectKey, purpose: 'open' as const })
         window.open(url, '_blank')
       } catch {
         toast.error('Failed to open file. It may have been deleted from storage.')

src/app/(applicant)/applicant/documents/page.tsx

@@ -46,11 +46,11 @@ const fileTypeLabels: Record<string, string> = {
 
 function FileActionButtons({ bucket, objectKey, fileName }: { bucket: string; objectKey: string; fileName: string }) {
   const { data: viewData } = trpc.file.getDownloadUrl.useQuery(
-    { bucket, objectKey, forDownload: false },
+    { bucket, objectKey, forDownload: false, purpose: 'open' as const },
     { staleTime: 10 * 60 * 1000 }
   )
   const { data: dlData } = trpc.file.getDownloadUrl.useQuery(
-    { bucket, objectKey, forDownload: true, fileName },
+    { bucket, objectKey, forDownload: true, fileName, purpose: 'download' as const },
     { staleTime: 10 * 60 * 1000 }
   )
   const viewUrl = typeof viewData === 'string' ? viewData : viewData?.url