feat: add Statuspage integration

[pranavrajs]

Adds the Statuspage integration (Engineering & status). Check Atlassian Statuspage incidents, component status, and planned maintenance.

Tools

• List Unresolved Incidents (list_unresolved_incidents, GET)
• List Components (list_components, GET)
• Search Incidents (search_incidents, GET)
• List Upcoming Maintenance (list_upcoming_maintenance, GET)
• List Active Maintenance (list_active_maintenance, GET)
• Get Incident (get_incident, GET)

Testing

• The manifest passes the validator ("valid": true).
• Every template was rendered locally with Liquid 5.4.0 against sample responses built from Statuspage's API docs.
• Not run against the live API. No credentials were available, so tool-tester.rb has not been run with a real key. This needs doing before merge.
• No logo is included.

Review notes

• Statuspage API keys are unscoped and carry the user's write access.
• Rate limit is 1 request per second per key.

The root README.md row and .env.example entry for this integration are in a separate PR, so the per-integration PRs do not conflict with each other.