feat: QR code scanning for gateway onboarding

iOS:
- QR scanner view using DataScannerViewController
- Photo library QR detection via CIDetector for saved QR images
- Deep link parser for openclaw://gateway URLs and base64url setup codes
- Onboarding wizard: full-screen welcome with "Scan QR Code" button,
  auto-connect on scan, back navigation, step indicators for manual flow

Backend:
- Add /pair qr action to device-pair extension for QR code generation
- TUI/WebUI differentiation: ASCII QR for TUI, markdown image for WebUI
- Telegram: send QR as media attachment via sendMessageTelegram
- Add data URI support to loadWebMedia for generic base64 media handling
- Export renderQrPngBase64 from plugin SDK for extension use

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
(cherry picked from commit d79ed65be0)

apps/shared/OpenClawKit/Sources/OpenClawKit/DeepLinks.swift

@@ -2,6 +2,56 @@ import Foundation
 
 public enum DeepLinkRoute: Sendable, Equatable {
     case agent(AgentDeepLink)
+    case gateway(GatewayConnectDeepLink)
+}
+
+public struct GatewayConnectDeepLink: Codable, Sendable, Equatable {
+    public let host: String
+    public let port: Int
+    public let tls: Bool
+    public let token: String?
+    public let password: String?
+
+    public init(host: String, port: Int, tls: Bool, token: String?, password: String?) {
+        self.host = host
+        self.port = port
+        self.tls = tls
+        self.token = token
+        self.password = password
+    }
+
+    public var websocketURL: URL? {
+        let scheme = self.tls ? "wss" : "ws"
+        return URL(string: "\(scheme)://\(self.host):\(self.port)")
+    }
+
+    /// Parse a device-pair setup code (base64url-encoded JSON: `{url, token?, password?}`).
+    public static func fromSetupCode(_ code: String) -> GatewayConnectDeepLink? {
+        guard let data = Self.decodeBase64Url(code) else { return nil }
+        guard let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else { return nil }
+        guard let urlString = json["url"] as? String,
+              let parsed = URLComponents(string: urlString),
+              let hostname = parsed.host, !hostname.isEmpty
+        else { return nil }
+
+        let scheme = parsed.scheme ?? "ws"
+        let tls = scheme == "wss"
+        let port = parsed.port ?? 18789
+        let token = json["token"] as? String
+        let password = json["password"] as? String
+        return GatewayConnectDeepLink(host: hostname, port: port, tls: tls, token: token, password: password)
+    }
+
+    private static func decodeBase64Url(_ input: String) -> Data? {
+        var base64 = input
+            .replacingOccurrences(of: "-", with: "+")
+            .replacingOccurrences(of: "_", with: "/")
+        let remainder = base64.count % 4
+        if remainder > 0 {
+            base64.append(contentsOf: String(repeating: "=", count: 4 - remainder))
+        }
+        return Data(base64Encoded: base64)
+    }
 }
 
 public struct AgentDeepLink: Codable, Sendable, Equatable {
@@ -69,6 +119,23 @@ public enum DeepLinkParser {
                     channel: query["channel"],
                     timeoutSeconds: timeoutSeconds,
                     key: query["key"]))
+
+        case "gateway":
+            guard let hostParam = query["host"],
+                  !hostParam.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
+            else {
+                return nil
+            }
+            let port = query["port"].flatMap { Int($0) } ?? 18789
+            let tls = (query["tls"] as NSString?)?.boolValue ?? false
+            return .gateway(
+                .init(
+                    host: hostParam,
+                    port: port,
+                    tls: tls,
+                    token: query["token"],
+                    password: query["password"]))
+
         default:
             return nil
         }