refactor: introduce Dependencies container and remove singletons

Targets/App/Sources/Main/Dependencies.swift

@@ -0,0 +1,21 @@
+import FlinkyCore
+import SwiftData
+
+@MainActor
+struct Dependencies {
+    let toastManager = ToastManager()
+    let appHealthObserver = AppHealthObserver()
+    let metricKitManager = MetricKitManager()
+
+    private let _modelContainer: LazyThrowingValue<ModelContainer>
+
+    var modelContainer: ModelContainer {
+        get throws { try _modelContainer.resolve() }
+    }
+
+    init(isTestingEnabled: Bool) {
+        _modelContainer = LazyThrowingValue {
+            try SharedModelContainerFactory.make(isStoredInMemoryOnly: isTestingEnabled)
+        }
+    }
+}

Targets/App/Sources/Main/FlinkyApp.swift

@@ -9,33 +9,32 @@ import os.log
 struct FlinkyApp: App {
     private static let logger = Logger.forType(Self.self)
 
-    private static let sharedToastManager = ToastManager()
-    @StateObject private var toastManager = FlinkyApp.sharedToastManager
-    private let sharedModelContainer: ModelContainer
+    private static let isTestingEnabled = ProcessInfo.processInfo.isTestingEnabled
+    private static let deps = Dependencies(isTestingEnabled: Self.isTestingEnabled)
+
+    @StateObject private var toastManager = Self.deps.toastManager
+    private let modelContainer: ModelContainer
 
     init() {
-        let isTestingEnabled = ProcessInfo.processInfo.isTestingEnabled
         SentrySDK.start { options in
-            Self.configureSentry(options: options, toastManager: Self.sharedToastManager, isTestingEnabled: isTestingEnabled)
+            Self.configureSentry(options: options, toastManager: Self.deps.toastManager, isTestingEnabled: Self.isTestingEnabled)
         }
 
         // Start app health observation for system-level metrics
         // (thermal state, network reachability, app state transitions)
-        AppHealthObserver.shared.startObserving()
+        Self.deps.appHealthObserver.startObserving()
 
         // Subscribe to MetricKit payloads and report all values as Sentry metrics
-        MetricKitManager.shared.startReceiving()
+        Self.deps.metricKitManager.startReceiving()
 
         do {
-            sharedModelContainer = try SharedModelContainerFactory.make(
-                isStoredInMemoryOnly: isTestingEnabled
-            )
+            modelContainer = try Self.deps.modelContainer
         } catch {
+            SentrySDK.capture(error: error)
             fatalError("Failed to create shared ModelContainer: \(error)")
         }
 
-        // Seed if needed on first app launch
-        DataSeedingService.seedDataIfNeeded(modelContext: sharedModelContainer.mainContext)
+        DataSeedingService.seedDataIfNeeded(modelContext: modelContainer.mainContext)
     }
 
     /// Configures the Sentry SDK options.
@@ -63,11 +62,11 @@ struct FlinkyApp: App {
         options.releaseName = "\(bundleId ?? "unknown")@\(version ?? "unknown")+\(build ?? "unknown")"
 
         func pickEnvValue<T>(production: T, develop: T) -> T {
-            #if DEBUG
-                return develop
-            #else
-                return production
-            #endif
+#if DEBUG
+            return develop
+#else
+            return production
+#endif
         }
         options.environment = pickEnvValue(production: "production", develop: "development")
 
@@ -247,6 +246,6 @@ struct FlinkyApp: App {
                     options.publicKey = "30d2f7cc2fa469eaf8e4bdf958ad9d66bce491a7da1fb08ff0a7156a8e15a47d"
                 }
         }
-        .modelContainer(sharedModelContainer)
+        .modelContainer(modelContainer)
     }
 }

Targets/App/Sources/Services/AppHealthObserver.swift

@@ -17,11 +17,6 @@ import UIKit
 /// Reference: https://github.com/getsentry/sentry-cocoa/issues/7000
 final class AppHealthObserver {
 
-    // MARK: - Singleton
-
-    /// Shared instance of the app health observer.
-    static let shared = AppHealthObserver()
-
     // MARK: - Properties
 
     private static let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "Flinky", category: "AppHealthObserver")
@@ -36,10 +31,6 @@ final class AppHealthObserver {
 
     private var isObserving = false
 
-    // MARK: - Initialization
-
-    private init() {}
-
     // MARK: - Public Methods
 
     /// Starts observing app health signals.

Targets/App/Sources/Services/MetricKitManager.swift

@@ -6,22 +6,12 @@ import SentrySwift
 
 final class MetricKitManager: NSObject, MXMetricManagerSubscriber {
 
-    // MARK: - Singleton
-
-    static let shared = MetricKitManager()
-
     // MARK: - Properties
 
     private static let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "Flinky", category: "MetricKitManager")
 
     private var isReceiving = false
 
-    // MARK: - Initialization
-
-    private override init() {
-        super.init()
-    }
-
     // MARK: - Public Methods
 
     func startReceiving() {

Targets/App/Sources/Utils/LazyThrowingValue.swift

@@ -0,0 +1,15 @@
+final class LazyThrowingValue<T> {
+    private var cached: T?
+    private let factory: () throws -> T
+
+    init(_ factory: @escaping () throws -> T) {
+        self.factory = factory
+    }
+
+    func resolve() throws -> T {
+        if let cached { return cached }
+        let value = try factory()
+        cached = value
+        return value
+    }
+}