Add MSX2J ROM and update manifests

Add MSX2J.rom (sha1: 0081ea0d25bc5cd8d70b60ad8cfdc7307812c0fd, size: 32768) to multiple install manifests and the RetroDECK bios list. Update generated timestamps and adjust total_files/total_size counts in batocera, lakka, recalbox, retroarch, retrobat, and retrodeck manifests. Also bump README verified file count and regenerate the auto-generated timestamp to reflect the new entry.

install/recalbox.json

@@ -4,7 +4,7 @@
   "platform": "recalbox",
   "display_name": "Recalbox",
   "version": "1.0",
-  "generated": "2026-04-01T14:42:39Z",
+  "generated": "2026-04-02T08:33:02Z",
   "base_destination": "bios",
   "detect": [
     {
@@ -15,8 +15,8 @@
     }
   ],
   "standalone_copies": [],
-  "total_files": 1097,
-  "total_size": 3500142330,
+  "total_files": 1098,
+  "total_size": 3500175098,
   "files": [
     {
       "dest": "3do/panafz1.bin",
@@ -851,6 +851,13 @@
       "repo_path": "bios/Microsoft/MSX/MSX2EXT.ROM",
       "cores": null
     },
+    {
+      "dest": "Machines/Shared Roms/MSX2J.rom",
+      "sha1": "0081ea0d25bc5cd8d70b60ad8cfdc7307812c0fd",
+      "size": 32768,
+      "repo_path": "bios/Microsoft/MSX/.variants/MSX2.ROM.0081ea0d",
+      "cores": null
+    },
     {
       "dest": "Machines/Shared Roms/MSX2P.rom",
       "sha1": "e90f80a61d94c617850c415e12ad70ac41e66bb7",