add the reorganize pages tool (#4506)

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

@@ -958,7 +958,7 @@
     "header": "PDF Page Organiser",
     "submit": "Rearrange Pages",
     "mode": {
-      "_value": "Mode",
+      "_value": "Organization mode",
       "1": "Custom Page Order",
       "2": "Reverse Order",
       "3": "Duplex Sort",
@@ -971,6 +971,19 @@
       "10": "Odd-Even Merge",
       "11": "Duplicate all pages"
     },
+    "desc": {
+      "CUSTOM": "Use a custom sequence of page numbers or expressions to define a new order.",
+      "REVERSE_ORDER": "Flip the document so the last page becomes first and so on.",
+      "DUPLEX_SORT": "Interleave fronts then backs as if a duplex scanner scanned all fronts, then all backs (1, n, 2, n-1, …).",
+      "BOOKLET_SORT": "Arrange pages for booklet printing (last, first, second, second last, …).",
+      "SIDE_STITCH_BOOKLET_SORT": "Arrange pages for side‑stitch booklet printing (optimised for binding on the side).",
+      "ODD_EVEN_SPLIT": "Split the document into two outputs: all odd pages and all even pages.",
+      "ODD_EVEN_MERGE": "Merge two PDFs by alternating pages: odd from the first, even from the second.",
+      "DUPLICATE": "Duplicate each page according to the custom order count (e.g., 4 duplicates each page 4×).",
+      "REMOVE_FIRST": "Remove the first page from the document.",
+      "REMOVE_LAST": "Remove the last page from the document.",
+      "REMOVE_FIRST_AND_LAST": "Remove both the first and last pages from the document."
+    },
     "placeholder": "(e.g. 1,3,2 or 4-8,2,10-12 or 2n-1)"
   },
   "addImage": {