Integrate Calamares graphical installer

[Anshgrover23]

Integrate Calamares as the primary graphical installer for Cortex Linux desktop installations, providing a modern, branded installation experience.

Current Behavior

• GRUB menu offers "Live Boot" or "Install" as separate options
• Installation uses stock Debian Installer (d-i)
• d-i has basic theming, looks dated
• No branded installation slideshow

Proposed Behavior

• Live boot is the default entry
• "Install Cortex Linux" desktop icon launches Calamares
• Calamares is fully themed with Cortex branding (dark theme, purple/cyan accents)
• Installation slideshow showcases Cortex features
• Keep d-i available in "Advanced Options" for server/automation use cases

GRUB Menu Structure

► Start Cortex Linux              ← Live desktop with Calamares icon
  Advanced Options ►
    └─ Install (Expert Mode)      ← d-i for automation/servers
    └─ Install (Text Mode)        ← For headless/SSH installs
    └─ Memory Test

Implementation Tasks

• Add calamares to package lists
• Create Calamares branding configuration (/etc/calamares/branding/cortex/)
  • branding.desc - metadata and strings
  • stylesheet.qss - dark theme matching Cortex colors
  • Logo and sidebar images
  • Installation slideshow (4-6 slides)
• Configure Calamares modules
  • welcome.conf - language selection
  • partition.conf - disk partitioning
  • users.conf - user creation
  • packages.conf - package selection (optional)
• Create desktop icon for installer
• Update GRUB menu entries
• Test on UEFI and BIOS systems
• Test on both amd64 and arm64

Design Requirements

Color Palette

• Background: #0F0F23 (dark)
• Primary: #6B21A8 (purple)
• Accent: #06B6D4 (cyan)
• Text: #E2E8F0 (light gray)

Slideshow Content Ideas

1. Welcome to Cortex Linux
2. AI-Ready Development Environment
3. Security by Default
4. Customization & Theming
5. Community & Support

References

• Calamares Documentation
• Calamares Branding Guide
• Manjaro Calamares Config (reference)

Priority

Medium - Improves user experience but current d-i works