Fix duplicate asset upload in release workflow

- Standalone binaries (pulse-sensor-proxy-*, pulse-host-agent-*) were matching both binaries AND .sha256 files
- .sha256 files already uploaded in 'Upload checksums.txt first' step
- gh release upload fails when same asset uploaded twice
- Fix: Use explicit loop to exclude .sha256, .tar.gz, and .zip extensions from standalone binary upload

Error was:
  asset under the same name already exists: [pulse-sensor-proxy-linux-386.sha256 ...]

Related to #671 (automated release workflow)

.github/workflows/release.yml

@@ -232,8 +232,12 @@ jobs:
 
           # Upload standalone binaries (for direct download by installers)
           echo "Uploading standalone binaries..."
-          gh release upload "${TAG}" release/pulse-sensor-proxy-*
-          gh release upload "${TAG}" release/pulse-host-agent-*
+          # Upload binaries without .sha256 files (those were already uploaded)
+          for file in release/pulse-sensor-proxy-* release/pulse-host-agent-*; do
+            if [[ ! "$file" =~ \.sha256$ ]] && [[ ! "$file" =~ \.tar\.gz$ ]] && [[ ! "$file" =~ \.zip$ ]]; then
+              gh release upload "${TAG}" "$file"
+            fi
+          done
 
       - name: Output release information
         run: |