Fix SwiftData migration crash on schema upgrades

Add = false/true defaults to all non-optional Bool properties so
SwiftData's lightweight migration knows what value to assign existing
rows. Replace try! ModelContainer with crash-safe do-catch that resets
the store on migration failure instead of crashing.

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

MealMood/Models/AppSettings.swift

@@ -4,11 +4,11 @@ import SwiftData
 @Model
 final class AppSettings {
     var mealWindows: String // "dinnerOnly", "lunchOnly", "both"
-    var includeWeekends: Bool
+    var includeWeekends: Bool = true
     var language: String // "spanish", "english"
 
     var calendarId: String?
-    var syncEnabled: Bool
+    var syncEnabled: Bool = false
     var syncMode: String? // "weekComplete", "manual"
     var lunchTime: Date
     var dinnerTime: Date
@@ -18,8 +18,8 @@ final class AppSettings {
     var iCloudSyncEnabled: Bool?
     var weekExportStyle: String?
 
-    var isPremium: Bool
-    var onboardingCompleted: Bool
+    var isPremium: Bool = false
+    var onboardingCompleted: Bool = false
 
     init() {
         self.mealWindows = "dinnerOnly"