Add Microsoft Teams notification channel

[renezander030]

What

Add Microsoft Teams as a notification/approval channel via incoming webhooks or the Bot Framework.

Why

Many businesses run on Teams, not Slack. Supporting Teams makes FixClaw viable for enterprise environments.

Scope

• Add a teams.go file
• Simplest path: use Teams incoming webhooks (Adaptive Cards for approve/reject buttons)
• Read teams_webhook_url from secrets.yaml
• Wire into the approval step type

Helpful context

• Teams incoming webhooks docs: https://learn.microsoft.com/en-us/microsoftteams/platform/webhooks-and-connectors/how-to/add-incoming-webhook
• Adaptive Cards for interactive buttons: https://adaptivecards.io/
• Follow the same pattern as the existing Slack integration