fix: align next/previous link layout with Material for MkDocs theme

[dushmanta05]

Fixes #799

Description

This PR fixes the misalignment in the docs footer where the “Next” / “Previous” text and their page titles were appearing too close together (inline instead of stacked).
It aligns the layout with the official Material for MkDocs theme.

To fix this, I moved the <span> element with the direction label (Next / Previous) outside of the .md-ellipsis div, so the label and title now stack properly.

I verified this against Astral Docs and other sites using the same theme.

Type of change

• New features (non-breaking change).
• Bug fix (non-breaking change).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).

Checklist

• I have performed a self-review of my code.
• I have added thorough tests if it is a core feature.
• There is a reference to the original bug report and related work.
• I have commented on my code, particularly in hard-to-understand areas.
• The feature is well documented.