migrate diagnosis screen to compose

app/src/main/java/com/nextcloud/talk/diagnose/AppBar.kt

@@ -0,0 +1,47 @@
+/*
+ * Nextcloud Talk - Android Client
+ *
+ * SPDX-FileCopyrightText: 2025 Marcel Hibbe <dev@mhibbe.de>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package com.nextcloud.talk.diagnose
+
+import androidx.activity.compose.LocalOnBackPressedDispatcherOwner
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.tooling.preview.Preview
+import com.nextcloud.talk.R
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun AppBar(title: String) {
+    val backDispatcher = LocalOnBackPressedDispatcherOwner.current?.onBackPressedDispatcher
+
+    TopAppBar(
+        title = { Text(text = title) },
+        navigationIcon = {
+            IconButton(
+                onClick = { backDispatcher?.onBackPressed() }
+            ) {
+                Icon(
+                    imageVector = Icons.AutoMirrored.Filled.ArrowBack,
+                    contentDescription = stringResource(R.string.back_button)
+                )
+            }
+        }
+    )
+}
+
+@Preview(showBackground = true)
+@Composable
+fun AppBarPreview() {
+    AppBar("title")
+}