Collapse 26 trivial single-package programs into home/programs/common.nix

Consolidates alacritty, audacity, blender, blockbench, claude-code, fd,
filezilla, fzf, gcc, godot_4, imv, jdk21, jetbrains-toolbox, lazygit,
lua-language-server, mpv, nil, nixpkgs-fmt, nodejs, obsidian, pkg-config,
prismlauncher, vesktop, xclip, xwallpaper, yt-dlp into a single list.

rustup.nix kept separate due to its configuration (session vars, many deps).

Updates imports:
- hivebrain: all 26 + rustup now via common.nix + rustup.nix
- nikita-nixos: blender.nix → common.nix (gets all lightweight tools)

hosts/nikita-nixos/home.nix

@@ -7,7 +7,7 @@
     ../../home/yazi.nix
     ../../home/symlinks.nix
     ../../home/packages-base.nix
-    ../../home/programs/blender.nix
+    ../../home/programs/common.nix
   ];
 
   home.username = "nikita";