refactor: reorganize flake structure and consolidate user config

Directory structure:
- Move from src/ to root level (system/, user/)
- Remove unused machines (workstation, vm, laptop)

User configuration:
- Add user/home.nix for shared defaults (pass, essentials, default modules)
- Centralize user options in user/default.nix
- Move submodules to consistent paths (bash/bash, git/git, neovim/nvim, vim/vim)

Module reorganization:
- Flatten nested module structures (remove /modules/ subdirs)
- Split CLI vs GUI tools (dev/ for CLI, gui/dev/ for GUI)
- Move neovim/vim to top-level modules (not under utils/)
- Remove security.enable - pass now in user/home.nix
- Remove utils.enable - essentials now in user/home.nix
- Add security/yubikey module with yubikey-manager, age-plugin-yubikey
- Move pcb, design to gui/dev/
- Replace penpot docker wrapper with nixpkgs penpot-desktop
- Remove i3 config
- Remove deprecated wsl.nativeSystemd option

GUI improvements:
- Browser-focused mimeApps in gui/default.nix
- Each WM handles its own auto-start via profileExtra

Cleanup:
- Update README with new structure
- Update justfile paths and valid systems
- Fix submodule paths in .gitmodules

system/machines/desktop/modules/home-manager/default.nix

@@ -0,0 +1,5 @@
+{
+  imports = [
+    ./home.nix
+  ];
+}

system/machines/desktop/modules/home-manager/home.nix

@@ -0,0 +1,54 @@
+{ config, ... }:
+
+{
+  home-manager.useGlobalPkgs = true;
+  home-manager.useUserPackages = true;
+  home-manager.extraSpecialArgs = {
+    monitors = config.monitors;
+  };
+  home-manager.users.${config.user.name} = {
+    imports = [
+      ../../../../../user
+      ../../../../../user/home.nix
+      ../../../../../user/modules
+    ];
+
+    home.stateVersion = "23.11";
+
+    programs.ssh = {
+      enable = true;
+      enableDefaultConfig = false;
+      matchBlocks = {
+        "*" = {
+          serverAliveInterval = 60;
+          serverAliveCountMax = 3;
+        };
+        "server" = {
+          hostname = "192.168.0.154";
+          user = "bryan";
+        };
+      };
+    };
+
+    # Machine-specific modules
+    modules.user = {
+      vim.enable = false;
+      security.yubikey.enable = true;
+
+      utils = {
+        dev.enable = true;
+        irc.enable = true;
+        writing.enable = true;
+      };
+
+      gui = {
+        wm.hyprland.enable = true;
+        browser.firefox.enable = true;
+        alacritty.enable = true;
+        corn.enable = true;
+        fun.enable = true;
+        utils.enable = true;
+      };
+    };
+  };
+}