mobile: tap the settings version footer to copy it (#9021)

## Summary

The version line at the bottom of mobile Settings (for example `v0.27.0
(36)`) couldn't be copied, which made it awkward to paste into bug
reports. Tapping it now copies the whole string and shows a "Version
copied" toast, matching the existing "Copy public key" row. It's
keyboard-focusable and has a 48dp tap target. Partial selection isn't
supported; it's whole-string only.

![Settings after tapping the version: a Version copied
toast](https://github.com/user-attachments/assets/007a10ed-61e5-47a2-b0a3-1f09f522e565)

### Related issue

N/A

### Validation

- Added test: tapping the footer, or reaching it with Tab and pressing
Enter, puts `v0.16.0 (432)` on the clipboard and shows the toast. The
test also checks that the tap target is at least 48dp tall.
- `just mobile-check` and `just mobile-test` pass.
- Automated simulator run (debug build, iOS 27): opened Settings, tapped
the version, confirmed via `simctl pbpaste` that the clipboard held the
exact footer text and the toast appeared; then confirmed the neighboring
"Copy public key" row still copies the npub and Settings still closes.
Human testing waived per the mobile testing exception. A full recording
was posted in Buzz instead of here because it shows internal channel
names.

🤖 Generated with [Claude Code](https://claude.com/claude-code)



buzz-review-completed

---------

Signed-off-by: Tom Brow <tomb@squareup.com>
Co-authored-by: Tom Brow <tomb@squareup.com>
Co-authored-by: studio <dc2fc481343672df31a689840c09299972e704dac592e0da6f18486646a7ee3e@buzz.block.builderlab.xyz>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

mobile/lib/features/settings/settings_page.dart

@@ -150,15 +150,41 @@ class _VersionFooter extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final label = buildNumber.isEmpty
+        ? 'v$version'
+        : 'v$version ($buildNumber)';
     return SafeArea(
       top: false,
-      child: Padding(
-        padding: const EdgeInsets.only(bottom: Grid.xs, top: Grid.xxs),
-        child: Center(
-          child: Text(
-            buildNumber.isEmpty ? 'v$version' : 'v$version ($buildNumber)',
-            style: context.textTheme.bodySmall?.copyWith(
-              color: context.colors.onSurfaceVariant.withValues(alpha: 0.6),
+      child: Center(
+        child: Semantics(
+          button: true,
+          onTapHint: 'Copy version',
+          child: InkWell(
+            borderRadius: BorderRadius.circular(Grid.xs),
+            onTap: () =>
+                copyToClipboard(context, label, message: 'Version copied'),
+            // Keep the text where it was and grow the tap target downward
+            // to the platform minimum.
+            child: ConstrainedBox(
+              constraints: const BoxConstraints(
+                minHeight: kMinInteractiveDimension,
+              ),
+              child: Padding(
+                padding: const EdgeInsets.fromLTRB(
+                  Grid.xs,
+                  Grid.xxs,
+                  Grid.xs,
+                  Grid.xs,
+                ),
+                child: Text(
+                  label,
+                  style: context.textTheme.bodySmall?.copyWith(
+                    color: context.colors.onSurfaceVariant.withValues(
+                      alpha: 0.6,
+                    ),
+                  ),
+                ),
+              ),
             ),
           ),
         ),

mobile/test/features/settings/settings_page_test.dart

@@ -92,6 +92,79 @@ void main() {
     });
   }
 
+  for (final viaKeyboard in [false, true]) {
+    testWidgets(
+      '${viaKeyboard ? 'keyboard activation of' : 'tapping'} the version copies the whole version string',
+      (tester) async {
+        String? copied;
+        tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+          SystemChannels.platform,
+          (call) async {
+            if (call.method == 'Clipboard.setData') {
+              copied = (call.arguments as Map)['text'] as String?;
+            }
+            return null;
+          },
+        );
+        addTearDown(
+          () => tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+            SystemChannels.platform,
+            null,
+          ),
+        );
+        SharedPreferences.setMockInitialValues({});
+        final prefs = await SharedPreferences.getInstance();
+        await tester.pumpWidget(
+          ProviderScope(
+            overrides: [savedPrefsProvider.overrideWithValue(prefs)],
+            child: MaterialApp(
+              theme: AppTheme.light(),
+              home: SettingsPage(
+                profileHeader: const SizedBox.shrink(),
+                identityRecoveryPageBuilder: (_) => const SizedBox.shrink(),
+              ),
+            ),
+          ),
+        );
+        await tester.pumpAndSettle();
+        final version = find.text('v0.16.0 (432)');
+        await tester.scrollUntilVisible(version, 200);
+        await tester.pumpAndSettle();
+        final target = find.ancestor(
+          of: version,
+          matching: find.byType(InkWell),
+        );
+        expect(
+          tester.getSize(target).height,
+          greaterThanOrEqualTo(kMinInteractiveDimension),
+        );
+
+        if (viaKeyboard) {
+          final versionFocus = Focus.of(tester.element(version));
+          var tabs = 0;
+          while (!versionFocus.hasPrimaryFocus) {
+            expect(
+              tabs++,
+              lessThan(50),
+              reason: 'version is not reachable by Tab',
+            );
+            await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+            await tester.pump();
+          }
+          await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+        } else {
+          await tester.tap(version);
+        }
+        await tester.pump();
+
+        expect(copied, 'v0.16.0 (432)');
+        expect(find.text('Version copied'), findsOneWidget);
+        await tester.pump(const Duration(seconds: 5));
+        await tester.pumpAndSettle();
+      },
+    );
+  }
+
   for (final outcome in ['absent', 'error']) {
     testWidgets('hides notifications while capability loads and is $outcome', (
       tester,