Add gitignore rules for build artifacts and binaries

Prevents server binaries, test binaries, and Unikraft build artifacts
from being committed to the repository.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: zshannon

.gitignore

@@ -201,3 +201,11 @@ custom-gcl.hash
 !internal/fourslash/_scripts/manualTests.txt
 
 .build
+
+# Server binaries
+server/server
+server/server-test
+node-bindings/test-musl
+
+# Unikraft build artifacts
+server/.unikraft/build/