Refactor UI: move Splits to Settings, redesign ExerciseView

Schema & Models:
- Add notes, loadType, duration fields to WorkoutLog
- Align Watch schema with iOS (use duration Date instead of separate mins/secs)
- Add duration helper properties to Exercise and WorkoutLog

UI Changes:
- Remove Splits and Settings tabs, single Workout Logs view
- Add gear button in nav bar to access Settings as sheet
- Move Splits section into Settings view with inline list
- Redesign ExerciseView with read-only Plan/Notes tiles and Edit buttons
- Add PlanEditView and NotesEditView with Cancel/Save buttons
- Auto-dismiss ExerciseView when completing last set
- Navigate to ExerciseView when adding new exercise

Data Flow:
- Plan edits sync to both WorkoutLog and corresponding Exercise
- Changes propagate up navigation chain via CoreData

Workouts Watch App/Models/Exercise.swift

@@ -21,6 +21,29 @@ public class Exercise: NSManagedObject, Identifiable {
         get { LoadType(rawValue: Int(loadType)) ?? .weight }
         set { loadType = Int32(newValue.rawValue) }
     }
+
+    // Duration helpers for minutes/seconds conversion
+    var durationMinutes: Int {
+        get {
+            guard let duration = duration else { return 0 }
+            return Int(duration.timeIntervalSince1970) / 60
+        }
+        set {
+            let seconds = durationSeconds
+            duration = Date(timeIntervalSince1970: TimeInterval(newValue * 60 + seconds))
+        }
+    }
+
+    var durationSeconds: Int {
+        get {
+            guard let duration = duration else { return 0 }
+            return Int(duration.timeIntervalSince1970) % 60
+        }
+        set {
+            let minutes = durationMinutes
+            duration = Date(timeIntervalSince1970: TimeInterval(minutes * 60 + newValue))
+        }
+    }
 }
 
 // MARK: - Fetch Request