feat: Configure Biome for Consistent Code Style

[shuoweil]

This PR adds biome.json to enforce consistent 2-space indentation and single quotes for JavaScript and CSS files. This aligns with project style guides, automates formatting via pre-commit hooks, and prevents manual style changes from being overwritten.

Currently, our Biome setup relies on default settings, which violates Google coding style guidelines. Specifically:

• Quotation Marks: Biome's defaults do not enforce single quotes for JavaScript (as per js_style.txt: screen/8NaEr3SswN6qx6D) and CSS property values (as per css_style.txt: screen/9KCh8ZVQ4ByPeDR).
• Indentation: Biome's defaults do not consistently enforce 2 spaces for indentation across HTML (screen/97ZZstQc4iH4Dsb) and JavaScript (screen/3crxm5peLvRE2kj) files.

This configuration explicitly sets these rules to ensure full compliance.

Benefits:

• Consistent and readable JS/CSS code.
• Automated style enforcement.
• Reduced developer friction.

To Test:
Make a style-violating change in a .js or .css file and attempt to commit. Biome should automatically reformat it.

Fixes #<issue_number_goes_here> 🦕