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/ContentView.swift

@@ -15,22 +15,7 @@ struct ContentView: View {
     @Environment(\.managedObjectContext) private var viewContext
 
     var body: some View {
-        TabView {
-            WorkoutLogsView()
-                .tabItem {
-                    Label("Workout Logs", systemImage: "list.bullet.clipboard")
-                }
-
-            SplitsView()
-                .tabItem {
-                    Label("Splits", systemImage: "dumbbell.fill")
-                }
-
-            SettingsView()
-                .tabItem {
-                    Label("Settings", systemImage: "gear")
-                }
-        }
+        WorkoutLogsView()
     }
 }