feat(wallet): Ark protocol support via barkd sidecar

barkd (Ark wallet daemon, pinned 0.3.0, checksum-verified release binary)
packaged as an installable app; thin HTTP bridge in wallet/ark_client.rs
mirrors the fedimint_client pattern — the bark SDK stays out of the node
binary. wallet.ark-* RPCs cover status/balance/address/send/invoice/
board/offboard/history/configure; Ark movements merge into the unified
ecash history (kind="ark") and spendable Ark sats into total_sats.
Signet defaults (Second's public Ark server) until Ark matures.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app-catalog/catalog.json

@@ -298,6 +298,25 @@
         ]
       }
     },
+    {
+      "id": "barkd",
+      "title": "Ark Wallet",
+      "version": "0.3.0",
+      "description": "Ark protocol wallet daemon (barkd). Lets the node hold self-custodial off-chain bitcoin via an Ark server; the wallet talks to it over a local REST API. Signet by default while Ark matures.",
+      "icon": "/assets/img/app-icons/bark.png",
+      "author": "Second",
+      "category": "money",
+      "dockerImage": "146.59.87.168:3000/lfg2025/barkd:0.3.0",
+      "repoUrl": "https://gitlab.com/ark-bitcoin/bark",
+      "containerConfig": {
+        "ports": [
+          "3535:3535"
+        ],
+        "volumes": [
+          "/var/lib/archipelago/barkd:/data"
+        ]
+      }
+    },
     {
       "id": "jellyfin",
       "title": "Jellyfin",