fix: correct logo white background to fill only inside the rounded square (#120)

## Summary
- Fixed the white background to properly fill only the interior of the
rounded square
- White glow now appears only on the outside edges as intended

## Technical Changes
- Changed the outer rounded square path from black to white fill
- Removed `filter="url(#whiteGlow)"` from all inner path elements
- Simplified the filter to create only external glow (no internal white
fill)
- Applied the glow filter only to the outer white square

## Result
The logo now has:
- Solid white background inside the entire rounded square
- Black design elements clearly visible on the white background  
- White glow effect only on the outside edges for visibility on dark
backgrounds

🤖 Generated with [Claude Code](https://claude.ai/code)

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Co-authored-by: Claude <noreply@anthropic.com>

Author: jwilger