feat: add UptimeRobot integration

[pranavrajs]

Adds the UptimeRobot integration (Engineering & status). Check UptimeRobot monitors and downtime incidents.

Tools

• List Down Monitors (list_down_monitors, GET)
• Search Monitors (search_monitors, GET)
• Get Monitor (get_monitor, GET)
• List Open Incidents (list_open_incidents, GET)
• List Recent Incidents (list_recent_incidents, GET)
• List Monitor Incidents (list_monitor_incidents, 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 UptimeRobot'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

• Uses the v3 API. Whether a read-only key is accepted as a v3 bearer token is unconfirmed.

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.