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

Cargo.lock

@@ -270,7 +270,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.59"
+version = "0.1.60"
 dependencies = [
  "anyhow",
  "chrono",
@@ -292,7 +292,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.59"
+version = "0.1.60"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -315,7 +315,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.59"
+version = "0.1.60"
 dependencies = [
  "chrono",
  "serde",