fix(mobile): auto-save watch directory on blur, not via Save button

The Save button is anchored to the Instance section near the top. Moving
the auto_import_path write to onBlur on the field itself means the value
is persisted as soon as the user leaves the input — no need to scroll up
and hit Save.

mobile/app/(tabs)/settings.tsx

@@ -37,9 +37,6 @@ export default function SettingsScreen() {
   async function save() {
     await setSetting(db, 'instance_url', instanceUrl.trim());
     await setSetting(db, 'handle', handle.trim());
-    if (Platform.OS === 'android') {
-      await setSetting(db, 'auto_import_path', autoPath.trim());
-    }
     setSaved(true);
     setTimeout(() => setSaved(false), 2000);
   }
@@ -173,11 +170,12 @@ export default function SettingsScreen() {
             placeholder="/sdcard/FitFiles"
             value={autoPath}
             onChangeText={setAutoPath}
+            onBlur={() => setSetting(db, 'auto_import_path', autoPath.trim())}
             autoCapitalize="none"
           />
           <Text style={styles.hint}>
-            New FIT files in this directory are imported automatically in the
-            background. Leave blank to disable. Requires storage permission.
+            New FIT files in this directory are imported automatically when you
+            open the app. Leave blank to disable. Requires storage permission.
           </Text>
         </Section>
       )}