Add Merge UI to V2 (#4235)

# Description of Changes
Add UI for Merge into V2.

frontend/public/locales/en-GB/translation.json

@@ -51,11 +51,11 @@
   "filesSelected": "{{count}} files selected",
   "files": {
     "title": "Files",
-    "placeholder": "Select a PDF file in the main view to get started",
     "upload": "Upload",
     "uploadFiles": "Upload Files",
     "addFiles": "Add files",
-    "selectFromWorkbench": "Select files from the workbench or "
+    "selectFromWorkbench": "Select files from the workbench or ",
+    "selectMultipleFromWorkbench": "Select at least {{count}} files from the workbench or "
   },
   "noFavourites": "No favourites added",
   "downloadComplete": "Download Complete",
@@ -644,11 +644,29 @@
   "merge": {
     "tags": "merge,Page operations,Back end,server side",
     "title": "Merge",
-    "header": "Merge multiple PDFs (2+)",
-    "sortByName": "Sort by name",
-    "sortByDate": "Sort by date",
-    "removeCertSign": "Remove digital signature in the merged file?",
-    "submit": "Merge"
+    "removeDigitalSignature": "Remove digital signature in the merged file?",
+    "generateTableOfContents": "Generate table of contents in the merged file?",
+    "removeDigitalSignature.tooltip": {
+      "title": "Remove Digital Signature",
+      "description": "Digital signatures will be invalidated when merging files. Check this to remove them from the final merged PDF."
+    },
+    "generateTableOfContents.tooltip": {
+      "title": "Generate Table of Contents",
+      "description": "Automatically creates a clickable table of contents in the merged PDF based on the original file names and page numbers."
+    },
+    "submit": "Merge",
+    "sortBy": {
+      "description": "Files will be merged in the order they're selected. Drag to reorder or sort below.",
+      "label": "Sort By",
+      "filename": "File Name",
+      "dateModified": "Date Modified",
+      "ascending": "Ascending",
+      "descending": "Descending",
+      "sort": "Sort"
+    },
+    "error": {
+      "failed": "An error occurred while merging the PDFs."
+    }
   },
   "split": {
     "tags": "Page operations,divide,Multi Page,cut,server side",