Description

Extend Calypso's simulation mode to allow specific topics to be selected and run on independent loop intervals, rather than simulating all topics at once.

Acceptance Criteria

• Topics to simulate are specifiable via flags at startup
• Each topic can be assigned its own loop interval (e.g. topic 1 every 30s, topic 2 every 10s)
• Only specified topics are published; all others are excluded
• Invalid topic names fail with a clear error

Proposed Solution

Extend src/bin/simulate.rs, reusing existing MQTT publish and topic generation code. Topics and their intervals are passed as flags. Add tests for topic filtering, per-topic interval behavior, and invalid topic handling.

Mocks

No response