Add complete GB translations for scanner image split tool

- Add scannerImageSplit section with submit/title/error translations
- Update home.scannerImageSplit title and description to match registry expectations
- Ensure all React component translation keys are properly supported
- Maintain British spelling ("colour") in existing translations

🤖 Generated with [Claude Code](https://claude.ai/code)

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

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

@@ -436,8 +436,8 @@
     },
     "scannerImageSplit": {
       "tags": "detect,split,photos",
-      "title": "Detect/Split Scanned photos",
-      "desc": "Splits multiple photos from within a photo/PDF"
+      "title": "Detect & Split Scanned Photos",
+      "desc": "Detect and split scanned photos into separate pages"
     },
     "sign": {
       "tags": "signature,autograph",
@@ -1668,6 +1668,13 @@
     },
     "info": "Python is not installed. It is required to run."
   },
+  "scannerImageSplit": {
+    "title": "Extracted Images",
+    "submit": "Extract Image Scans",
+    "error": {
+      "failed": "An error occurred while extracting image scans."
+    }
+  },
   "sign": {
     "title": "Sign",
     "header": "Sign PDFs",