Add ical dependency & implement VTODO iCalendar Feed (/api/schedule/feed.ics)

[allenporter]

Integrate the ical Python package to export user tasks as RFC 5545 VTODO objects via /api/schedule/feed.ics.

[allenporter]

Implementation Plan

Technical Overview

Export tasks managed in Supernote's Schedule service (ScheduleTaskDO) into RFC 5545 compliant VTODO iCalendar feeds using the ical Python library, enabling live task subscriptions in Apple Reminders, Google Calendar, Todoist, and E-ink sync workflows.

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Proposed Changes

1. Dependencies

• Add "ical>=8.0.0" under [project.optional-dependencies] server in pyproject.toml.

2. Domain & Conversion Service (ical_export.py)

• Define ICalExportService:
  • Map ScheduleTaskDO and ScheduleTaskGroupDO records into ical.calendar.Calendar and ical.todo.Todo instances.
  • Field Mapping:
    • summary: task.title
    • description: task.detail
    • uid: f"supernote-task-{task.task_id}@supernote"
    • due: UTC datetime / date from task.due_time
    • status: ical.types.TodoStatus.COMPLETED or TodoStatus.NEEDS_ACTION
    • completed: UTC datetime from task.completed_time
    • categories: [group.title] (e.g. ["Inbox"])
  • Serialize using ical.calendar_stream.ICalendarStream.calendar_to_ical(calendar).

3. Authentication & REST API Endpoint (schedule.py)

• Implement GET /api/schedule/feed.ics:
  • Accepts session auth OR ?token=<feed_token> query parameter (enabling native Apple Calendar / Reminders subscriptions without header limitations).
  • Optional taskListId query parameter to filter by a specific task list/group.
  • Returns HTTP 200 with Content-Type: text/calendar; charset=utf-8.

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Verification Plan

Automated Tests

1. Unit Test (tests/server/test_schedule_ical.py): Verify ICalExportService.export_calendar() returns valid RFC 5545 string output containing BEGIN:VCALENDAR, BEGIN:VTODO, SUMMARY, STATUS, DUE, UID. Parse returned .ics back with ical.calendar_stream.ICalendarStream.calendar_from_ical() to verify round-trip fidelity.
2. Route Test (tests/server/test_schedule_routes.py): Test GET /api/schedule/feed.ics returns HTTP 200 and Content-Type: text/calendar; charset=utf-8.