Surface SIMKL calendar v2 finale markers in Up Next

[Copilot]

SIMKL calendar data now ships as v2 payloads with UTC timestamps and episode-level finale_type markers. This updates the existing SIMKL episode import / up-next flow to retain those fields and expose finale badges in the dashboard.

• SIMKL episode import

  • Parse UTC episode air timestamps from SIMKL payloads into EpisodeItem.air_date
  • Preserve episode finale_type in stored SIMKL raw payloads
  • Keep the importer compatible with existing SIMKL item shapes while retaining the new calendar-derived fields

• Up Next API payload

  • Extend episode_to_payload() to include finale_type
  • Read finale_type from persisted episode raw data, handling both numeric and string values

• Dashboard UI

  • Render finale badges in the Up Next row:
    • 1 → Mid-season finale
    • 2 → Season finale
    • 3 → Series finale

• Regression coverage

  • Add focused tests for SIMKL episode air-date parsing and finale marker preservation
  • Extend next-episode payload tests to cover finale_type serialization

def episode_to_payload(episode: EpisodeItem) -> dict:
    return {
        "episode_item_id": episode.id,
        "season_number": episode.season_number,
        "episode_number": episode.episode_number,
        "title": episode.title,
        "air_date": episode.air_date.isoformat() if episode.air_date else None,
        "finale_type": _episode_finale_type(episode),
    }

• Fixes Trakt calendar updates #99