Add Warm-Up and Stretching activity types

Adds WorkoutActivityType.warmUp (HealthKit .preparationAndRecovery) and
.stretching (.flexibility), and retags the six starter splits that were all
mislabeled as Functional Strength:

- Warm-Up:    Upper Body Warm-Up, Lower Body Warm-Up, Morning Wake-Up
- Stretching: Morning Mobility, Full Body Stretch, Evening Stretch

The split editor's activity picker surfaces them automatically (CaseIterable).
Older app versions decode the new raw values as the default type — additive and
not schema-gated, so no quarantine.

project.yml

@@ -14,6 +14,7 @@ settings:
     MARKETING_VERSION: "2.3"
     CURRENT_PROJECT_VERSION: "1"
     ENABLE_USER_SCRIPT_SANDBOXING: "NO"
+    DEAD_CODE_STRIPPING: "YES"
 
 packages:
   IndieAbout: