Enforce 44×44 dp touch targets on all interactive elements

Prefer ButtonStyle.minimumSize (Size(44, 44)) for ElevatedButton and TextButton components — this is the idiomatic Flutter approach and avoids adding extra wrapper widgets. For text-only links rendered as a TextSpan inside a Text.rich, wrap the tappable span in a GestureDetector with a SizedBox(width: double.infinity, height: 44) or use a ConstrainedBox. Do not use Padding alone to increase tap area — padding does not contribute to hit-testing on all widget types. Test on a physical device or emulator at 1× DPI after implementing to confirm the tap zone feels comfortable.

Note that the 44 dp minimum applies to both width AND height independently — a wide but short button (e.g., 200×36 dp) still fails and needs the height increased. Use the accessible-touch-target-wrapper pattern as a shared widget if multiple locations across the app need this treatment, to avoid repeating the boilerplate.

Extend the widget test suite with a group 'touch_targets'. For each interactive element: (1) pump the widget, (2) use tester.getSize(find.byKey(Key('portal-link-touch-target'))) and assert width >= 44 and height >= 44, (3) repeat for the logout button. Also call meetsGuideline(androidTapTargetGuideline) and meetsGuideline(iOSTapTargetGuideline) on the full widget. Integration: tap the portal link touch zone at its corner coordinate and assert the url_launcher mock receives the correct URL.

Tap the logout button at the edge and assert the sign-out BLoC event fires.