Add native macOS folder picker for staging directory

Uses AWT FileDialog with apple.awt.fileDialogForDirectories=true to open
the native macOS folder chooser. Falls back gracefully (dialog cancelled)
with no change to the text field.

src/main/kotlin/com/bolenpad/photophetch/ui/SettingsScreen.kt

@@ -3,12 +3,16 @@ package com.bolenpad.photophetch.ui
 import androidx.compose.foundation.layout.*
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.FolderOpen
 import androidx.compose.material3.*
 import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
+import java.awt.FileDialog
+import java.awt.Frame
+import java.io.File
 
 @Composable
 fun SettingsScreen(state: AppState) {
@@ -33,14 +37,30 @@ fun SettingsScreen(state: AppState) {
 
         // Staging directory
         Text("Staging Directory", style = MaterialTheme.typography.titleSmall, fontWeight = FontWeight.SemiBold)
+        Row(
+            horizontalArrangement = Arrangement.spacedBy(8.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
             OutlinedTextField(
                 value = stagingRoot,
                 onValueChange = { stagingRoot = it },
                 label = { Text("Path to _staging/ directory") },
                 placeholder = { Text("/Volumes/delphi/_staging") },
-            modifier = Modifier.fillMaxWidth(),
+                modifier = Modifier.weight(1f),
                 singleLine = true,
             )
+            OutlinedIconButton(
+                onClick = {
+                    val chosen = pickFolder(
+                        title = "Select _staging directory",
+                        initialDir = stagingRoot.ifBlank { "/Volumes" },
+                    )
+                    if (chosen != null) stagingRoot = chosen
+                },
+            ) {
+                Icon(Icons.Default.FolderOpen, contentDescription = "Browse…")
+            }
+        }
         Text(
             "This should be the _staging directory on your NAS (must be mounted).",
             style = MaterialTheme.typography.bodySmall,
@@ -78,7 +98,6 @@ fun SettingsScreen(state: AppState) {
         Button(
             onClick = {
                 state.updateStagingRoot(stagingRoot)
-                // Also save template update
                 state.saveConfig()
             },
             modifier = Modifier.fillMaxWidth().height(52.dp),
@@ -87,3 +106,24 @@ fun SettingsScreen(state: AppState) {
         }
     }
 }
+
+/**
+ * Opens the native macOS folder picker (System.setProperty trick to make
+ * AWT FileDialog show directories instead of files).
+ * Returns the chosen absolute path, or null if cancelled.
+ */
+private fun pickFolder(title: String, initialDir: String): String? {
+    // On macOS, this system property switches FileDialog to directory-selection mode
+    System.setProperty("apple.awt.fileDialogForDirectories", "true")
+    return try {
+        val dialog = FileDialog(null as Frame?, title, FileDialog.LOAD).apply {
+            directory = initialDir
+            isVisible = true
+        }
+        val dir = dialog.directory
+        val file = dialog.file
+        if (file != null) File(dir, file).absolutePath else null
+    } finally {
+        System.setProperty("apple.awt.fileDialogForDirectories", "false")
+    }
+}