Feat/custom notification

[CodingWithTashi]

feat: custom notification system with deep-link navigation

• Added custom notification sound (routine.ogg / routine.caf) for both Android and iOS
• Created NotificationChannels registry — single source of truth for all channel config
• Refactored NotificationService: split init from permission request, added router/container refs for navigation
• Notification tap now deep-links directly to the relevant practice item (recitation or plan)
• Handles all 3 app states: foreground, background, and terminated (cold launch)
• RoutineNotificationService now encodes itemId/itemType as JSON payload in each scheduled notification
• New NotificationSettingsScreen: master toggle, per-channel toggle, exact alarms, battery optimization
• Added unit tests for NotificationChannels and RoutineNotificationService
• Fixed iOS CodeMagic build issues