feat: redesign payment targets modal with QR, copy and pay buttons

Each target now renders in a single row with the payment method and
address on the left and three trailing icon buttons: QR (opens a dialog
showing the raw address as a QR code), Copy (clipboard + toast), and
Pay (existing payto:// intent). Adds QrCode2 to MaterialSymbols.

https://claude.ai/code/session_01JtJuvSYMusKiDMWo7N8Aj8

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/MaterialSymbols.kt

@@ -175,6 +175,7 @@ object MaterialSymbols {
     val Public = MaterialSymbol("\uE80B")
     val PublicOff = MaterialSymbol("\uF1CA")
     val PushPin = MaterialSymbol("\uF10D")
+    val QrCode2 = MaterialSymbol("\uEF6B")
     val RadioButtonChecked = MaterialSymbol("\uE837")
     val RadioButtonUnchecked = MaterialSymbol("\uE836")
     val Recommend = MaterialSymbol("\uE9D2")