Bug: repo_info endpoint missing graph_exists() check

[gkorland]

Description

The repo_info endpoint in api/index.py creates a Graph(repo) and calls g.stats() without first checking graph_exists(repo):

@app.route('/api/repo_info', methods=['POST'])
@public_access
@token_required
def repo_info():
    data = request.get_json()
    repo = data.get('repo')
    if repo is None:
        return jsonify({'status': 'Missing mandatory parameter "repo"'}), 400

    g = Graph(repo)        # No graph_exists() check
    stats = g.stats()
    info = get_repo_info(repo)
    ...

Other endpoints like graph_entities, get_neighbors, and find_paths all check graph_exists(repo) before proceeding.

Suggested Fix

Add the same guard:

if not graph_exists(repo):
    return jsonify({'status': f'Missing project {repo}'}), 400

Context

Found during code review of PR #522.

[JiwaniZakir]

The inconsistency likely crept in when repo_info was added or refactored separately from the other endpoints, without the graph_exists() guard being treated as a required pattern. Without the check, Graph(repo) will instantiate a graph object against a non-existent graph, and g.stats() will either return meaningless/empty data or raise an exception depending on how the underlying FalkorDB client handles missing graphs — neither of which produces a clean 400 response to the caller. The fix is straightforward: add if not graph_exists(repo): return jsonify({'status': f'Missing project {repo}'}), 400 in api/index.py immediately after the repo is None guard in the repo_info function, consistent with how graph_entities, get_neighbors, and find_paths handle this case.