feat(events): add Postscript /api/v2/events client support

[jcartwright]

Summary

• Add Postscript.Event.create/1 for Custom Events (POST /api/v2/events), with operations baking in http_path: "/api/v2" so callers cannot accidentally hit /v1/events
• Leave existing /v1 Trigger/Subscriber/Keyword APIs and default http_path unchanged; 202 Accepted + event_ids already succeeds via existing request handling
• Bump to 1.1.0 and target the private Malomo Hex org (organization: "malomo") for publish after merge

Test plan

• CI green (test + dialyzer matrix)
• Confirm Event.create/1 URL is https://api.postscript.io/api/v2/events without passing http_path to Postscript.request/2
• Confirm Trigger (and other v1) requests still use /v1
• After merge: mix hex.publish as a Malomo org member; verify 1.1.0 on the Malomo org packages dashboard
• Point integration-postscript at {:postscript, "~> 1.1", organization: "malomo"}

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