Update app icon with new gradient heart design

[Copilot]

Replaced the existing Tahoe-style liquid glass icon with a new gradient heart design featuring orange/peach → pink → purple color transition with white border.

Changes

• assets/icon.svg - New gradient heart SVG with 7-stop color progression and soft shadow
• assets/icon.png - Regenerated 1024×1024 PNG via existing build script
• README.md - Updated icon descriptions (removed "Tahoe-style liquid glass" references)

Icon Design

• Gradient: #FFD4A8 (peach) → #FF6699 (pink) → #8866DD (purple)
• White stroke: 10px with rounded joins
• Soft shadow: 20px blur, 12px Y-offset, 35% opacity

Usage

Icon is referenced in:

• Favicon (HTML)
• Loading screen (HTML)
• Window icon (Electron)
• Dock icon (macOS)
• App bundle + DMG (electron-builder)

Preview

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Update the app icon everywhere it is used in the repository.

The new icon to use is attached below.

This pull request was created from Copilot chat.

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