feat: Configure Biome for Consistent Code Style (#2364)

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> 🦕

Author: shuoweil

biome.json

@@ -0,0 +1,16 @@
+{
+  "formatter": {
+    "indentStyle": "space",
+    "indentWidth": 2
+  },
+  "javascript": {
+    "formatter": {
+      "quoteStyle": "single"
+    }
+  },
+  "css": {
+    "formatter": {
+      "quoteStyle": "single"
+    }
+  }
+}