fix: adjust markdown spacing to prevent text overlap

[lemorage]

Description

In the markdown component, the parent <div> in markdown.tsx applies the classes prose-ul:-my-2 prose-ol:-my-2 prose-li:-my-2, which set negative margins on HTML list elements.

In markdown.css, the rule .prose li p { margin-top: -19px; } reduces the space between the <p> inside a <li> and the preceding content, causing overlap.

This PR tries to fix these problems, and so resolves #2451.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested by running the mem0 demo, and chatting with the bots. The markdown rendering works properly now, as shown in the pic.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed