Changes

• Added features/tourney/tourney_reports.py — new TourneyReports Cog with a monthly auto-report that runs on the 1st of each month at 06:00 UTC, reading from
  #tourney-reports to aggregate per-tourney embeds for the previous month
• Added /monthly-report [month] [year] slash command for staff to manually trigger or retroactively generate monthly reports, with live ephemeral status updates and
  specific error messages at each failure point
• Added TOURNEY_REPORT_CHANNEL_ID and TOURNEY_SCHEDULE_CHANNEL_ID to config.py for both PROD and DEV
• Updated !endtourney to send the tournament report to both #tourney-admin and #tourney-reports with no pinning; report now includes the tourney name (from
  Matcherino API) as a hyperlinked title, canonical tournament date (from #tourney-schedule), staff pings (<@user_id>) instead of usernames, and a Matcherino ID footer
• Updated !starttourney to auto-detect the Matcherino ID by scanning #tourney-schedule for an announcement within ±1 day of today, with detailed error messages
  explaining exactly why detection failed if it does

Screenshots

Tourney Reports in dedicated channel & Monthly Report aggregates tourney reports from the month:

Tourney announcement in tourney schedule channel (sent by user, parsed by the bot):

!starttourney reads from tourney schedule and auto detects tourney id:

Tourney Report embed updated if there is a tourney id:

Closes #312