[Enhancement] More complex example

Motivation

This FR arises from discussion in #527 about the healthcare example, which is very clear and helpful for demonstrating basic functionality but seems to be less helpful for showcasing Parlant's more advanced features. A further, more complex, sample may reduce potential duplication of effort in future issues and FRs.

Solution Proposal

Create another example that highlights the flexibility and advanced features Parlant offers, ideally with well-documented code that walks users through aspects of the design process.

Discussion

A good set of examples with various levels of complexity can be seen in the Rio Templates. Live demos for some examples are available here.

For an example of confusion that may arise when creating samples, see rio#207.