fix: remove accidentally committed .o build artifact

A 68MB object file was committed to the repo. Remove it and add
*.o / *.a / *.d patterns to .gitignore to prevent recurrence.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ovitrif

.gitignore

@@ -24,6 +24,11 @@ swift.swiftdoc
 # Ignore LDKNodeFFI.xcframework files
 /bindings/swift/LDKNodeFFI.xcframework
 
+# Build artifacts
+*.o
+*.a
+*.d
+
 # IDE and local files
 .idea
 .build