fix: align backend commit response with frontend expectations

Backend was returning fields like 'author', 'email', 'date' but frontend
expected 'author_name', 'author_email', 'author_date'. Also 'branches' and
'tags' were separate but frontend expects unified 'refs' array.

- Update _commit_to_dict to return frontend-compatible field names
- Add graph_symbol and graph_depth for commit graph display
- Update get_commit_detail to return matching field names
- Include diff as top-level field for detail view

apps/api/src/utils/git_history.py

@@ -114,11 +114,26 @@ def get_commit_history(repo_path: str, branch: str | None = None, limit: int = 1
     count_output = _run_git_command(repo_path, ["rev-list", "--all", "--count"])
     total_commits = int(count_output.strip()) if count_output.strip() else 0
 
-    # Build graph data
+    # Build graph data and generate graph symbols
     graph_data = _build_graph_data(commits)
+    
+    # Generate simple graph symbols based on parent count
+    commit_dicts = []
+    for i, commit in enumerate(commits):
+        if len(commit.parents) == 0:
+            graph_symbol = "○"  # Initial commit
+        elif len(commit.parents) > 1:
+            graph_symbol = "●"  # Merge commit
+        else:
+            graph_symbol = "○"  # Regular commit
+        
+        # Simple depth calculation based on merge status
+        graph_depth = min(len(commit.parents), 3)
+        
+        commit_dicts.append(_commit_to_dict(commit, graph_symbol, graph_depth))
 
     return {
-        "commits": [_commit_to_dict(c) for c in commits],
+        "commits": commit_dicts,
         "branches": branches,
         "total_commits": total_commits,
         "graph_data": graph_data,
@@ -165,15 +180,18 @@ def get_commit_detail(repo_path: str, commit_hash: str) -> dict[str, Any]:
         "hash": commit_hash,
         "short_hash": commit_hash[:7],
         "parents": parents,
-        "author": author,
-        "email": email,
-        "date": str(timestamp),
-        "timestamp": timestamp,
+        "author_name": author,
+        "author_email": email,
+        "author_date": str(timestamp),
+        "committer_name": author,  # TODO: extract committer separately
+        "committer_email": email,  # TODO: extract committer separately
+        "committer_date": str(timestamp),
         "message": message,
         "body": body,
         "branches": branch_map.get(commit_hash, []),
         "tags": tag_map.get(commit_hash, []),
         "stats": stats,
+        "diff": diff_output,
         "files": [_file_change_to_dict(f) for f in files],
     }
 
@@ -329,19 +347,25 @@ def _parse_diff(diff_output: str) -> list[FileChange]:
     return files
 
 
-def _commit_to_dict(commit: Commit) -> dict[str, Any]:
+def _commit_to_dict(commit: Commit, graph_symbol: str = "", graph_depth: int = 0) -> dict[str, Any]:
     """Convert Commit dataclass to dictionary."""
+    refs = []
+    if commit.branches:
+        refs.extend(commit.branches)
+    if commit.tags:
+        refs.extend(commit.tags)
+    
     return {
         "hash": commit.hash,
         "short_hash": commit.short_hash,
         "parents": commit.parents,
-        "author": commit.author,
-        "email": commit.email,
-        "date": commit.date,
-        "timestamp": commit.timestamp,
+        "author_name": commit.author,
+        "author_email": commit.email,
+        "author_date": str(commit.timestamp),
         "message": commit.message,
-        "branches": commit.branches,
-        "tags": commit.tags,
+        "refs": refs,
+        "graph_symbol": graph_symbol,
+        "graph_depth": graph_depth,
     }