Fix flaky UI tests: increase calendar wait timeouts and disable parallel UI testing

Calendar navigation buttons used shortTimeout (5s) which was too tight under
simulator load, causing cascading failures in wizard and trip saving tests.
Bumped to defaultTimeout (15s) and disabled parallel execution for UI tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SportsTime.xcodeproj/xcshareddata/xcschemes/SportsTime.xcscheme

@@ -43,7 +43,7 @@
          </TestableReference>
          <TestableReference
             skipped = "NO"
-            parallelizable = "YES">
+            parallelizable = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "1CA7F90D2F0D647400490ABD"