feat: add merchant profile panel to Merchant tab

Display merchant profile information with:
- Banner image or grey placeholder
- Profile avatar with shadow
- Display name (or name fallback)
- About description
- NIP-05 verified identity indicator
- Lightning address (LUD16)

Extends MerchantProfile model with new fields:
display_name, banner, nip05, lud16

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/components/key-pair.js

@@ -2,21 +2,10 @@ window.app.component('key-pair', {
   name: 'key-pair',
   template: '#key-pair',
   delimiters: ['${', '}'],
-  props: ['public-key', 'private-key'],
-  data: function () {
-    return {
-      showPrivateKey: false
-    }
-  },
+  props: ['public-key', 'private-key', 'merchant-config'],
   methods: {
-    copyText: function (text, message, position) {
-      var notify = this.$q.notify
-      Quasar.copyToClipboard(text).then(function () {
-        notify({
-          message: message || 'Copied to clipboard!',
-          position: position || 'bottom'
-        })
-      })
+    handleImageError: function (event) {
+      event.target.style.display = 'none'
     }
   }
 })

static/components/merchant-tab.js

@@ -10,7 +10,8 @@ window.app.component('merchant-tab', {
     'merchant-active',
     'public-key',
     'private-key',
-    'is-admin'
+    'is-admin',
+    'merchant-config'
   ],
   computed: {
     marketClientUrl: function () {