Move away from Homebrew packages to Nix packages

[delafthi]

Goal

Replace all Homebrew-managed packages with Nix equivalents to maintain a fully reproducible system configuration.

Current State

Currently using Homebrew to manage cask applications (see system/darwin/user/homebrew.nix).

Progress

Remaining Packages

Not in nixpkgs:

• Migrate gog-galaxy from Homebrew to Nix #96 - gog-galaxy
• Migrate proton-drive from Homebrew to Nix #103 - proton-drive

Broken on darwin:

• Migrate blender from Homebrew to Nix #94 - blender
• Migrate karabiner-elements from Homebrew to Nix #97 - karabiner-elements (nix-darwin service broken)
• Migrate kicad from Homebrew to Nix #98 - kicad

Platform limitations:

• Migrate steam from Homebrew to Nix #106 - steam (NixOS module only)
• Migrate wacom-tablet from Homebrew to Nix #109 - wacom-tablet (only Linux)

Successfully Migrated

• Migrate discord from Homebrew to Nix #95 - discord
• Migrate obsidian from Homebrew to Nix #102 - obsidian
• Migrate signal from Homebrew to Nix #105 - signal
• Migrate transmission from Homebrew to Nix #108 - transmission (unmaintained in nixpkgs)
• Migrate zen from Homebrew to Nix #110 - zen (experimental darwin implementation)
• Migrate alcove from Homebrew to Nix #93 - alcove
• Migrate subler from Homebrew to Nix #107 - subler
• Migrate lunar from Homebrew to Nix #99 - lunar
• Migrate meetingbar from Homebrew to Nix #100 - meetingbar
• Migrate monodraw from Homebrew to Nix #101 - monodraw
• Migrate protonvpn from Homebrew to Nix #104 - protonvpn (only Linux)