refactor(ios): dedupe gateway helpers

apps/ios/Sources/Gateway/GatewaySetupCode.swift

@@ -0,0 +1,42 @@
+import Foundation
+
+struct GatewaySetupPayload: Codable {
+    var url: String?
+    var host: String?
+    var port: Int?
+    var tls: Bool?
+    var token: String?
+    var password: String?
+}
+
+enum GatewaySetupCode {
+    static func decode(raw: String) -> GatewaySetupPayload? {
+        if let payload = decodeFromJSON(raw) {
+            return payload
+        }
+        if let decoded = decodeBase64Payload(raw),
+           let payload = decodeFromJSON(decoded)
+        {
+            return payload
+        }
+        return nil
+    }
+
+    private static func decodeFromJSON(_ json: String) -> GatewaySetupPayload? {
+        guard let data = json.data(using: .utf8) else { return nil }
+        return try? JSONDecoder().decode(GatewaySetupPayload.self, from: data)
+    }
+
+    private static func decodeBase64Payload(_ raw: String) -> String? {
+        let trimmed = raw.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty else { return nil }
+        let normalized = trimmed
+            .replacingOccurrences(of: "-", with: "+")
+            .replacingOccurrences(of: "_", with: "/")
+        let padding = normalized.count % 4
+        let padded = padding == 0 ? normalized : normalized + String(repeating: "=", count: 4 - padding)
+        guard let data = Data(base64Encoded: padded) else { return nil }
+        return String(data: data, encoding: .utf8)
+    }
+}
+