feat: add Public chip to onchain wallet card

The onchain wallet's Taproot address is derived from the account's Nostr
pubkey, so anyone with the npub can see its balance and transaction
history on-chain. Surface that fact directly on the card with a tappable
"(i) Public" chip that opens a dialog explaining the privacy implication
and recommending private (non-Nostr) channels for funding and draining.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/wallet/OnchainSection.kt

@@ -35,6 +35,7 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Card
@@ -43,6 +44,7 @@ import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
@@ -180,6 +182,8 @@ private fun HeaderRow(
                     style = MaterialTheme.typography.titleMedium,
                     fontWeight = FontWeight.SemiBold,
                 )
+                Spacer(modifier = Modifier.width(8.dp))
+                PublicChip()
             }
             Spacer(modifier = Modifier.height(4.dp))
             Text(
@@ -193,6 +197,65 @@ private fun HeaderRow(
     }
 }
 
+@Composable
+private fun PublicChip() {
+    var showDialog by remember { mutableStateOf(false) }
+    val onSurfaceVariant = MaterialTheme.colorScheme.onSurfaceVariant
+
+    Row(
+        modifier =
+            Modifier
+                .clip(RoundedCornerShape(8.dp))
+                .background(onSurfaceVariant.copy(alpha = 0.12f))
+                .clickable { showDialog = true }
+                .padding(horizontal = 6.dp, vertical = 2.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Icon(
+            symbol = MaterialSymbols.Info,
+            contentDescription = null,
+            tint = onSurfaceVariant,
+            modifier = Modifier.size(12.dp),
+        )
+        Spacer(modifier = Modifier.width(4.dp))
+        Text(
+            text = "Public",
+            style = MaterialTheme.typography.labelSmall,
+            color = onSurfaceVariant,
+            fontWeight = FontWeight.Medium,
+        )
+    }
+
+    if (showDialog) {
+        AlertDialog(
+            onDismissRequest = { showDialog = false },
+            icon = {
+                Icon(
+                    symbol = MaterialSymbols.Info,
+                    contentDescription = null,
+                    modifier = Modifier.size(24.dp),
+                )
+            },
+            title = { Text("This wallet is public") },
+            text = {
+                Text(
+                    "Your Taproot address is derived from your Nostr public key, " +
+                        "so anyone who knows your npub can see this wallet's balance " +
+                        "and transaction history on the blockchain.\n\n" +
+                        "To preserve your privacy, use private channels — not Nostr " +
+                        "events — when funding or draining this wallet, and avoid " +
+                        "linking deposits or withdrawals to identifiable activity.",
+                )
+            },
+            confirmButton = {
+                TextButton(onClick = { showDialog = false }) {
+                    Text("Got it")
+                }
+            },
+        )
+    }
+}
+
 @Composable
 private fun BitcoinChip(orange: Color) {
     Box(

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

@@ -129,6 +129,7 @@ object MaterialSymbols {
     val HourglassEmpty = MaterialSymbol("\uE88B")
     val HourglassTop = MaterialSymbol("\uEA5B")
     val Image = MaterialSymbol("\uE3F4")
+    val Info = MaterialSymbol("\uE88E")
     val Key = MaterialSymbol("\uE73C")
     val KeyboardArrowDown = MaterialSymbol("\uE313")
     val KeyboardArrowUp = MaterialSymbol("\uE316")