Add Apple Reminders capture feature

[liketheduck]

Summary

• Enables importing tasks from Apple Reminders into Taskchamp via a new "Reminders Capture" settings panel
• Users can select a specific Reminders list to capture from (e.g., "Taskchamp Inbox")
• Supports Siri integration - say "Hey Siri, remind me to..." and import into Taskchamp
• Configurable post-import action: mark complete or delete from Apple Reminders
• Automatic import when app becomes active with duplicate prevention

Changes

• RemindersCaptureService: EventKit integration for fetching/importing reminders
• RemindersCaptureSettingsView: SwiftUI settings UI with permission handling, list picker, and manual import
• ContentView: Auto-import on app foreground
• TaskListView: Menu item + sheet for settings, auto-refresh after import
• Project.swift: Added NSRemindersUsageDescription for permission prompt
• UserDefaults: Added keys for reminders capture settings persistence

Test plan

• Grant Reminders permission when prompted
• Select a Reminders list in settings
• Create a reminder in Apple Reminders app
• Return to Taskchamp - verify automatic import
• Verify reminder marked complete/deleted in Apple Reminders
• Verify duplicate prevention (re-import doesn't create duplicates)

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