Add expandedSql property to Statement for debugging

[smith-xyz]

Summary

Adds expandedSql property to Statement objects for debugging SQL with/without bound parameters.

Description

Exposes SQLite's sqlite3_expanded_sql() as a readonly property accessor on Statement. Returns the SQL query with parameter values filled in, useful for debugging and logging actual queries.

Example Usage

const stmt = db.prepare("SELECT * FROM users WHERE id = ?");
stmt.get(123, function(err, row) {
  console.log(stmt.expandedSql); 
  // "SELECT * FROM users WHERE id = 123"
});

Changes

• Added ExpandedSQLGetter() N-API property accessor to Statement class
• Proper memory management with sqlite3_free()
• TypeScript definitions updated
• Tests added

Closes #1678