MCP_expense_tracer

The `summarize_expenses` function contains a critical bug where it attempts to append strings to a `sqlite3.Cursor` object (`query += ...`), leading to a `TypeError` if a category is provided. While this specific bug prevents the code from executing the problematic string concatenation, it indicates poor SQL query construction. If this bug were 'fixed' by building the SQL query string via concatenation *without* proper parameterization, it *would* introduce a SQL injection vulnerability for the `category` parameter. Other functions (`add_expense`, `list_expenses`) correctly use parameterized queries, mitigating immediate SQL injection risks for those operations. The server is designed for local use with no apparent hardcoded secrets or explicit network exposures beyond its local FastMCP interface.