Skip rig maintenance alert when all rigs are up to date

[Copilot]

Currently, the rig maintenance check sends a Slack notification regardless of whether maintenance is needed, including a "🎉 All rig maintenance is up to date!" message when everything is current. This creates notification noise when no action is required.

Changes

• Added conditional check in check_rig_maintenance.py to skip Slack notification when overdue_items is empty
• Only alerts are sent when rigs have overdue or upcoming maintenance that requires attention

# Before
send_slack_notification(overdue_items, current_date)

# After  
if overdue_items:
    current_date = datetime.now().date()
    send_slack_notification(overdue_items, current_date)

Exit codes remain unchanged (0 when up to date, 1 when issues exist).

Original prompt

Update the rig maintenance alert to only send out if the amount of rigs needing or will need maintenance is 0. If total is 0 don't send 0

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