fix: correct binary file detection in git file viewer

- Remove useless git diff --numstat call that failed in bare repos
- Use raw bytes instead of text decoding to avoid encoding issues
- Properly check subprocess return codes

Fixes false positive binary detection for text files like .env.sample

apps/api/src/utils/git_files.py

@@ -190,18 +190,17 @@ def get_file_content(repo_path: str, branch: str, path: str) -> FileContent:
 
 
 def _is_binary_file(repo_path: str, branch: str, path: str) -> bool:
-    """Check if a file is binary."""
+    """Check if a file is binary using raw bytes to avoid encoding issues."""
     try:
-        _run_git_command(
-            repo_path,
-            "diff",
-            "--numstat",
-            "--",
-            path,
+        result = subprocess.run(
+            ["git", "show", f"{branch}:{path}"],
+            cwd=repo_path,
+            capture_output=True,
         )
-        # Alternative: use git show and check for null bytes
-        content = _run_git_command(repo_path, "show", f"{branch}:{path}")
-        return b"\x00" in content.encode("utf-8", errors="replace")
+        if result.returncode != 0:
+            raise RuntimeError(f"Git command failed: {result.stderr.decode()}")
+        # A file is binary if it contains null bytes
+        return b"\x00" in result.stdout
     except RuntimeError:
         return True