Process crash via non-enforcing parser depth limit

Denial of service in Scriban 6.6.0 through 7.2.0 allows attackers to crash the host process via deeply nested template expressions. In src/Scriban/Parsing/Parser.Expressions.cs, EnterExpression increments depth and logs an error when ExpressionDepthLimit is exceeded, but it neither aborts parsing nor unwinds recursion, so ParseExpression continues through nested parentheses, arrays, objects, and unary operators until .NET raises an uncatchable StackOverflowException. Exposure requires attacker influence over template text passed to Template.Parse or Template.ParseLiquid, or over strings re-parsed by object.eval or object.eval_template; the consequence is bounded to availability because the process terminates immediately.