Wip/new tutorial agents

[nomeforme]

Description

The main changes are:

• removed langchain, because if the goal is just to show usage of nvm payments + observability vs vanilla then langchain is extra complexity. so the simple openai api call is used, and message history is just a simple array.
• changed the system prompt from being about "real time market data" to being about a financial educational advisor, because for this to be accurate tool calling with market data should be implemented
• made some readability improvements and added tutorial style comments above all the main functions

Is this PR related with an open issue?

Related to Issue #

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Follows the code style of this project.
• Tests Cover Changes
• Documentation