Add app icon asset, screenshot exporter, and misc updates

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

Shared/Persisence/DataControllerHelper.swift

@@ -79,6 +79,29 @@ extension DataController {
         saveAndRunDataListeners()
     }
 
+    #if DEBUG
+    func populate2YearsData() {
+        clearDB()
+
+        for idx in 1...730 {
+            let date = Calendar.current.date(byAdding: .day, value: -idx, to: Date())!
+            var moodValue = Int.random(in: 3...4)
+            if Int.random(in: 0...400) % 5 == 0 {
+                moodValue = Int.random(in: 0...4)
+            }
+
+            let entry = MoodEntryModel(
+                forDate: date,
+                mood: Mood(rawValue: moodValue) ?? .average,
+                entryType: .listView
+            )
+            modelContext.insert(entry)
+        }
+
+        saveAndRunDataListeners()
+    }
+    #endif
+
     func longestStreak() -> [MoodEntryModel] {
         let descriptor = FetchDescriptor<MoodEntryModel>(
             sortBy: [SortDescriptor(\.forDate, order: .forward)]