chore: remove deprecated Pulse+ agent metrics and add audit log rotation docs

Removed all legacy Pulse+ agent metrics infrastructure (cloud-relay) which has been
fully replaced by the new docker agent and temperature agent implementations.

Changes:
- Remove cloud-relay directory and all related binaries (relay, relay-linux, etc.)
- Remove Pulse+ documentation (AGENT_METRICS_IMPLEMENTATION.md, AGENT_METRICS_SETUP.md)
- Clean up pulse-relay references in workflows and release checklist
- Add audit log rotation documentation for sensor proxy hash-chained logs
- Update .gitignore to remove cloud-relay/ entry

The new docker and temp agents remain fully functional and unaffected by this cleanup.

.github/workflows/README.md

@@ -4,7 +4,7 @@
 
 **File**: `update-demo-server.yml`
 
-Automatically updates the public demo server (`pulse-relay`) when a new stable release is published.
+Automatically updates the public demo server when a new stable release is published.
 
 ### Configuration Required
 
@@ -38,11 +38,6 @@ To test without publishing a release:
 2. Select `Update Demo Server` workflow
 3. Click `Run workflow` (if manual trigger is enabled)
 
-Or test manually:
-```bash
-ssh pulse-relay "curl -fsSL https://raw.githubusercontent.com/rcourtman/Pulse/main/install.sh | sudo bash"
-```
-
 ### Benefits
 
 - ✅ Demo server always showcases latest stable release