Fix Tab key 1-second delay by reverting ZMQ to non-blocking mode

- Change receive_metrics() from blocking to DONTWAIT to prevent main loop freezing
- Eliminate 1-second ZMQ socket timeout that was blocking UI after Tab key press
- Main loop now continues immediately after immediate render instead of waiting
- Maintain heartbeat-based host detection while fixing visual responsiveness
- Fix blocking operation introduced when implementing heartbeat timeout mechanism
- Tab navigation now truly immediate without any network operation delays
- Bump version to 0.1.61

shared/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-shared"
-version = "0.1.60"
+version = "0.1.61"
 edition = "2021"
 
 [dependencies]