fix(settings): use Save as the primary label on settings form dialogs (#1571)

ui/flutter/lib/features/settings/presentation/widgets/download_categories_setting.dart

@@ -201,7 +201,7 @@ Future<DownloadCategoryDraft?> showDownloadCategoryDialog(
               onPressed: () => shad.closeOverlay(dialogContext),
               child: Text(dialogContext.l10n.cancel),
             ),
-            AppPrimaryButton(onPressed: submit, child: Text(dialogContext.l10n.confirm)),
+            AppPrimaryButton(onPressed: submit, child: Text(dialogContext.l10n.save)),
           ],
         );
       },

ui/flutter/lib/features/settings/presentation/widgets/settings_list_editor.dart

@@ -234,7 +234,7 @@ Future<String?> showTextSettingDialog(
                 }
                 shad.closeOverlay(dialogContext, controller.text.trim());
               },
-              child: Text(dialogContext.l10n.confirm),
+              child: Text(dialogContext.l10n.save),
             ),
           ],
         );
@@ -321,7 +321,7 @@ Future<GithubMirrorDraft?> showGithubMirrorDialog(BuildContext context, {GithubM
                 }
                 shad.closeOverlay(dialogContext, GithubMirrorDraft(type: selectedType, url: value));
               },
-              child: Text(dialogContext.l10n.confirm),
+              child: Text(dialogContext.l10n.save),
             ),
           ],
         );

ui/flutter/test/widget_test.dart

@@ -2480,7 +2480,7 @@ void main() {
     expect(find.text('%date% — Full date (YYYY-MM-DD)'), findsOneWidget);
     await tester.tap(find.byKey(const ValueKey('path-placeholder-%date%')));
     await tester.pumpAndSettle();
-    await tester.tap(find.text('Confirm'));
+    await tester.tap(find.text('Save'));
     await tester.pumpAndSettle();
 
     expect(find.text('归档'), findsOneWidget);