feat: add theme-adaptive favicon

- Replace full logo (1875x1699) with simplified icon (512x512) optimized for favicon display
- Implement CSS media queries for automatic theme adaptation:
  * Dark mode: white X (#FFFFFF) with cyan dot (#34CCCD)
  * Light mode: dark blue X and dot (#1D3865)
- Remove old logo files (xpeditis-icon.svg, xpeditis-logo.svg)
- Simplified design with clean X shape and accent dot for better visibility at small sizes

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/frontend/public/assets/logos/xpeditis-icon.svg

@@ -1,5 +0,0 @@
-<svg width="48" height="48" viewBox="0 0 48 48" fill="none" xmlns="http://www.w3.org/2000/svg">
-  <rect width="48" height="48" rx="8" fill="#10183A"/>
-  <path d="M14 14L34 34M34 14L14 34" stroke="#34CCCD" stroke-width="4" stroke-linecap="round"/>
-  <circle cx="24" cy="24" r="3" fill="#34CCCD"/>
-</svg>

apps/frontend/public/assets/logos/xpeditis-logo.svg

@@ -1,11 +0,0 @@
-<svg width="180" height="48" viewBox="0 0 180 48" fill="none" xmlns="http://www.w3.org/2000/svg">
-  <!-- Icon/Symbol -->
-  <rect width="48" height="48" rx="8" fill="#10183A"/>
-  <path d="M14 14L34 34M34 14L14 34" stroke="#34CCCD" stroke-width="4" stroke-linecap="round"/>
-  <circle cx="24" cy="24" r="3" fill="#34CCCD"/>
-
-  <!-- Text "XPEDITIS" -->
-  <text x="58" y="34" font-family="Manrope, sans-serif" font-size="24" font-weight="700" fill="#10183A" letter-spacing="-0.5">
-    XPEDITIS
-  </text>
-</svg>