feat(android): typed-confirm on AdminUsers delete (audit v3 §4.20)

Delete-user was a plain Delete/Cancel AlertDialog — too permissive
for an irreversible action. Now mirrors Flutter's TypedConfirmSheet:
an OutlinedTextField where the admin must type "DELETE" before the
Delete button enables (case-insensitive). The button stays disabled
and muted until the word matches.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/admin/ui/AdminUsersScreen.kt

@@ -512,18 +512,41 @@ private fun DeleteConfirmDialog(
     onDismiss: () -> Unit,
     onConfirm: () -> Unit,
 ) {
+    var typed by remember { mutableStateOf("") }
+    val confirmed = typed.trim().equals(DELETE_CONFIRM_WORD, ignoreCase = true)
     AlertDialog(
         onDismissRequest = onDismiss,
         title = { Text("Delete user?") },
         text = {
-            Text("Delete @${user.username}? This removes the account and all their data.")
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text(
+                    "Delete @${user.username}? This removes the account and all " +
+                        "their data. Type $DELETE_CONFIRM_WORD to confirm.",
+                )
+                OutlinedTextField(
+                    value = typed,
+                    onValueChange = { typed = it },
+                    label = { Text("Type $DELETE_CONFIRM_WORD") },
+                    singleLine = true,
+                    modifier = Modifier.fillMaxWidth(),
+                )
+            }
         },
         confirmButton = {
-            TextButton(onClick = onConfirm) {
+            TextButton(onClick = onConfirm, enabled = confirmed) {
-                Text("Delete", color = MaterialTheme.colorScheme.error)
+                Text(
+                    "Delete",
+                    color = if (confirmed) {
+                        MaterialTheme.colorScheme.error
+                    } else {
+                        MaterialTheme.colorScheme.onSurfaceVariant
+                    },
+                )
             }
         },
         dismissButton = { TextButton(onClick = onDismiss) { Text("Cancel") } },
     )
 }
 
+private const val DELETE_CONFIRM_WORD = "DELETE"
+