Initial Bobink library: BobinkAuth, BobinkClient, and demo app

Implements the core OPC UA wrapper library with:
- Build system with automatic dep building (open62541, QtOpcUa)
- BobinkAuth: QML auth component (anonymous/userpass/certificate)
- BobinkClient: QML singleton managing connection, LDS discovery,
  PKI configuration, endpoint selection, and certificate trust flow
- Demo app for manual testing of the full connection flow

1 files changed, 188 insertions, 0 deletions

diff --git a/demo/Main.qml b/demo/Main.qml
new file mode 100644
index 0000000..6d1327d
--- /dev/null
+++ b/demo/Main.qml
@@ -0,0 +1,188 @@
+import QtQuick
+import QtQuick.Controls
+import QtQuick.Layouts
+import Bobink
+
+ApplicationWindow {
+    width: 600
+    height: 600
+    visible: true
+    title: "Bobink Demo"
+
+    Connections {
+        target: BobinkClient
+        function onServersChanged() {
+            console.log("Discovered server list updated")
+        }
+        function onConnectedChanged() {
+            console.log("Connected:", BobinkClient.connected)
+        }
+        function onConnectionError(message) {
+            console.log("Connection error:", message)
+        }
+        function onDiscoveringChanged() {
+            console.log("Discovering:", BobinkClient.discovering)
+        }
+    }
+
+    ColumnLayout {
+        anchors.fill: parent
+        anchors.margins: 20
+        spacing: 12
+
+        Label { text: "Discovery URL"; font.bold: true }
+
+        RowLayout {
+            TextField {
+                id: discoveryUrlField
+                Layout.fillWidth: true
+                text: "opc.tcp://localhost:4840"
+            }
+            Button {
+                text: BobinkClient.discovering ? "Stop" : "Discover"
+                onClicked: {
+                    if (BobinkClient.discovering) {
+                        BobinkClient.stopDiscovery()
+                    } else {
+                        BobinkClient.discoveryUrl = discoveryUrlField.text
+                        BobinkClient.startDiscovery()
+                    }
+                }
+            }
+        }
+
+        Label {
+            text: BobinkClient.discovering
+                  ? "Discovering... (" + BobinkClient.servers.length + " found)"
+                  : BobinkClient.servers.length + " server(s)"
+            font.italic: true
+        }
+
+        ListView {
+            Layout.fillWidth: true
+            Layout.preferredHeight: 100
+            clip: true
+            model: BobinkClient.servers
+            delegate: ItemDelegate {
+                width: ListView.view.width
+                text: modelData.serverName + "  —  " + modelData.applicationUri
+                onClicked: {
+                    if (modelData.discoveryUrls.length > 0)
+                        serverUrlField.text = modelData.discoveryUrls[0]
+                }
+            }
+            ScrollBar.vertical: ScrollBar {}
+        }
+
+        Label { text: "PKI Directory"; font.bold: true }
+
+        RowLayout {
+            TextField {
+                id: pkiDirField
+                Layout.fillWidth: true
+                text: BobinkClient.pkiDir
+                onEditingFinished: BobinkClient.pkiDir = text
+            }
+            Button {
+                text: "Apply PKI"
+                onClicked: {
+                    BobinkClient.pkiDir = pkiDirField.text
+                    BobinkClient.applyPki()
+                    console.log("PKI applied:", BobinkClient.pkiDir)
+                }
+            }
+        }
+
+        Label { text: "Server URL"; font.bold: true }
+
+        RowLayout {
+            TextField {
+                id: serverUrlField
+                Layout.fillWidth: true
+                placeholderText: "opc.tcp://..."
+            }
+        }
+
+        Label { text: "Authentication"; font.bold: true }
+
+        BobinkAuth {
+            id: auth
+            mode: {
+                switch (authModeCombo.currentIndex) {
+                case 0: return BobinkAuth.Anonymous
+                case 1: return BobinkAuth.UserPass
+                case 2: return BobinkAuth.Certificate
+                default: return BobinkAuth.Anonymous
+                }
+            }
+            username: usernameField.text
+            password: passwordField.text
+            certPath: certPathField.text
+            keyPath: keyPathField.text
+        }
+
+        ComboBox {
+            id: authModeCombo
+            Layout.fillWidth: true
+            model: ["Anonymous", "Username / Password", "Certificate"]
+        }
+
+        GridLayout {
+            columns: 2
+            visible: authModeCombo.currentIndex === 1
+            Layout.fillWidth: true
+
+            Label { text: "Username:" }
+            TextField {
+                id: usernameField
+                Layout.fillWidth: true
+            }
+            Label { text: "Password:" }
+            TextField {
+                id: passwordField
+                Layout.fillWidth: true
+                echoMode: TextInput.Password
+            }
+        }
+
+        GridLayout {
+            columns: 2
+            visible: authModeCombo.currentIndex === 2
+            Layout.fillWidth: true
+
+            Label { text: "Certificate:" }
+            TextField {
+                id: certPathField
+                Layout.fillWidth: true
+                placeholderText: "/path/to/cert.pem"
+            }
+            Label { text: "Private key:" }
+            TextField {
+                id: keyPathField
+                Layout.fillWidth: true
+                placeholderText: "/path/to/key.pem"
+            }
+        }
+
+        Button {
+            text: BobinkClient.connected ? "Disconnect" : "Connect"
+            Layout.fillWidth: true
+            onClicked: {
+                if (BobinkClient.connected) {
+                    BobinkClient.disconnectFromServer()
+                } else {
+                    BobinkClient.auth = auth
+                    BobinkClient.serverUrl = serverUrlField.text
+                    BobinkClient.connectToServer()
+                }
+            }
+        }
+
+        Label {
+            text: "Status: " + (BobinkClient.connected ? "Connected" : "Disconnected")
+            color: BobinkClient.connected ? "green" : "red"
+        }
+
+        Item { Layout.fillHeight: true }
+    }
+}