Replace newWindow SVG with enhanced design

[alaricholt677]

New Icon

I noticed the previous Windows icon was too basic and not visually aligned with the Fluent/Windows 11 aesthetic.
This updated SVG introduces:

• Soft Fluent-style drop shadow
• Four-tile Windows layout
• Premium Win11 blue gradients per tile
• Proper rounded corners
• 48×48 Fluent grid alignment

Here is the corrected and valid SVG:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 48 48" width="48" height="48">
  <defs>
    <!-- Soft Drop Shadow Filter -->
    <filter id="taskbar-glow" x="-20%" y="-20%" width="140%" height="140%">
      <feDropShadow dx="0" dy="1.5" stdDeviation="1.2" flood-color="#000000" flood-opacity="0.25"/>
    </filter>

    <!-- Premium Fluent Gradients -->
    <linearGradient id="win11-blue-top-left" x1="10%" y1="10%" x2="90%" y2="90%">
      <stop offset="0%" stop-color="#4da2ff"/>
      <stop offset="100%" stop-color="#0066e6"/>
    </linearGradient>

    <linearGradient id="win11-blue-top-right" x1="10%" y1="10%" x2="90%" y2="90%">
      <stop offset="0%" stop-color="#3399ff"/>
      <stop offset="100%" stop-color="#0052cc"/>
    </linearGradient>

    <linearGradient id="win11-blue-bottom-left" x1="10%" y1="10%" x2="90%" y2="90%">
      <stop offset="0%" stop-color="#1a8cff"/>
      <stop offset="100%" stop-color="#003db3"/>
    </linearGradient>

    <linearGradient id="win11-blue-bottom-right" x1="10%" y1="10%" x2="90%" y2="90%">
      <stop offset="0%" stop-color="#0073e6"/>
      <stop offset="100%" stop-color="#002b80"/>
    </linearGradient>
  </defs>

  <!-- Main Icon Grid with Rounded Corners and Lighting Shadows -->
  <g filter="url(#taskbar-glow)">
    <!-- Top Left Tile -->
    <rect x="5" y="5" width="18" height="18" rx="2.5" fill="url(#win11-blue-top-left)"/>
    <!-- Top Right Tile -->
    <rect x="25" y="5" width="18" height="18" rx="2.5" fill="url(#win11-blue-top-right)"/>
    <!-- Bottom Left Tile -->
    <rect x="5" y="25" width="18" height="18" rx="2.5" fill="url(#win11-blue-bottom-left)"/>
    <!-- Bottom Right Tile -->
    <rect x="25" y="25" width="18" height="18" rx="2.5" fill="url(#win11-blue-bottom-right)"/>
  </g>
</svg>