chore: updating fonts from centrano1 to geist (#586)

### Description
This PR updates the Snaps Directory typography to use the Geist font
family instead of CentraNo1, aligning with recent decisions from [design
leadership and branding
team](https://consensys.slack.com/archives/C0354T27M5M/p1750203008207359)
to standardize on Geist across MetaMask products.

### Changes Made

#### Font Assets
- ✅ **Added** Geist font files:
  - `Geist-Regular.woff2` (400 weight)
  - `Geist-RegularItalic.woff2` (400 weight italic)
  - `Geist-Medium.woff2` (500 weight)
  - `Geist-MediumItalic.woff2` (500 weight italic)
  - `Geist-Bold.woff2` (700 weight)
  - `Geist-BoldItalic.woff2` (700 weight italic)

- ❌ **Removed** CentraNo1 font files:
  - `CentraNo1-Book.woff2`
  - `CentraNo1-Book-Italic.woff2`
  - `CentraNo1-Medium.woff2`
  - `CentraNo1-Medium-Italic.woff2`
  - `CentraNo1-Bold.woff2`
  - `CentraNo1-Bold-Italic.woff2`

#### Configuration Updates
- **`src/assets/fonts/fonts.css`**: Updated all `@font-face`
declarations to use `'Geist'` family name and new font file paths
- **`src/theme/fonts.ts`**: Updated body font stack from `"Centra No1"`
to `"Geist"`
- **`src/theme/index.test.ts`**: Updated test expectations to reflect
new font family

### Font Weight Mapping
| Weight | Regular | Italic |
|--------|---------|--------|
| 400 | Geist-Regular.woff2 | Geist-RegularItalic.woff2 |
| 500 | Geist-Medium.woff2 | Geist-MediumItalic.woff2 |
| 700 | Geist-Bold.woff2 | Geist-BoldItalic.woff2 |

### Impact
- **Visual**: Users will see improved typography with the Geist font
family
- **Branding**: Aligns Snaps Directory with MetaMask's updated design
system
- **Performance**: No significant impact on bundle size (similar font
file sizes)
- **Accessibility**: Maintains same font weights and styles for
consistent readability

### Testing
- ✅ All existing tests updated and passing
- ✅ Font rendering verified across different weights and styles
- ✅ Typography remains consistent across the application

## Screenhots/Screencast

### Before


https://github.com/user-attachments/assets/cfad4ec9-ffa1-4b99-b367-208349a7d557

### After


https://github.com/user-attachments/assets/179f41ac-3048-4800-b101-0ba0e553e3ea

Author: georgewrmarshall