fix: remove accidentally committed test binary and restore .gitignore

- Remove backend/repository.test (62MB macOS arm64 test binary)
- Restore *.test pattern in .gitignore to prevent future accidents

.gitignore

@@ -14,6 +14,9 @@ backend/server
 backend/sub2api
 backend/main
 
+# Go 测试二进制
+*.test
+
 # 测试覆盖率
 *.out
 coverage.html