release(catalog): clear the legacy btcpay 2.3.9 entry — signed

The legacy `btcpay` entry (distinct from `btcpay-server`, no embedded manifest)
still carried a concrete 2.3.9 image. catalog_primary_image treats that as
authoritative, which is what drove the UI to offer "update to 2.3.9" on nodes
already running 2.4.2 — a rollback onto the actively exploited release.

Now 2.4.2 in both entries, signed by the pinned release root and verified.

This lands the fix for every node immediately, without waiting for the binary
carrying the downgrade guard (cbfda305) to reach them. The guard remains the
durable fix: it makes any future stale pin fail safe rather than relying on
every version claim being correct.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

releases/app-catalog.json

@@ -858,13 +858,13 @@
       "version": "1.2.11"
     },
     "btcpay": {
-      "image": "docker.io/btcpayserver/btcpayserver:2.3.9",
+      "image": "docker.io/btcpayserver/btcpayserver:2.4.2",
       "images": {
         "archy-btcpay-db": "146.59.87.168:3000/lfg2025/postgres:15.17",
         "archy-nbxplorer": "146.59.87.168:3000/lfg2025/nbxplorer:2.6.0",
-        "btcpay-server": "docker.io/btcpayserver/btcpayserver:2.3.9"
+        "btcpay-server": "docker.io/btcpayserver/btcpayserver:2.4.2"
       },
-      "version": "2.3.9"
+      "version": "2.4.2"
     },
     "btcpay-server": {
       "manifest": {
@@ -4897,7 +4897,7 @@
     }
   },
   "schema": 1,
-  "signature": "532eb226558e175cbb7c0aa307d0cc1800ed0794266795d817509ab29fcd7334383e33c257552f7e29ba033e99205b6b73285b88e06d79f2d6096629d6471109",
+  "signature": "0ccba6b8bb26fc718ad126049f96b5800109949770d894fa4ff6c947871cf6c8779c1c474d39ccf886708842cfbbf2e57cb904092bde8f8a65163acd7f3ff401",
   "signed_by": "did:key:z6Mkfu5LT8d4DjETtrkATvHh9Dvcbnr7zBCUwfau8Sw7DLWT",
   "updated": "2026-08-07"
 }