feat(branding): professionalize installer and system branding

- Refactor installer with Gum for a professional interactive experience
- Create custom Nomarchy Plymouth theme with centered logo
- Establish assets/branding directory for official logos and ASCII art
- Update Fastfetch config with official ASCII art and declarative stats
- Declaratively link branding assets via Home Manager

config/fastfetch/config.jsonc

@@ -2,7 +2,7 @@
   "$schema": "https://github.com/fastfetch-cli/fastfetch/raw/dev/doc/json_schema.json",
   "logo": {
     "type": "file",
-    "source": "~/.config/nomarchy/branding/about.txt",
+    "source": "~/.config/nomarchy/branding/logo.txt",
     "color": { "1": "green" },
     "padding": {
       "top": 2,
@@ -63,22 +63,9 @@
       "format": "\u001b[90m┌──────────────────────Software──────────────────────┐"
     },
     {
-      "type": "command",
+      "type": "os",
       "key": "\ue900 OS",
-      "keyColor": "blue",
-      "text": "version=$(nomarchy-version); echo \"Nomarchy $version\""
-    },
-    {
-      "type": "command",
-      "key": "│ ├󰘬",
-      "keyColor": "blue",
-      "text": "branch=$(nomarchy-version-branch); echo \"$branch\""
-    },
-    {
-      "type": "command",
-      "key": "│ ├󰔫",
-      "keyColor": "blue",
-      "text": "channel=$(nomarchy-version-channel); echo \"$channel\""
+      "keyColor": "blue"
     },
     {
       "type": "kernel",
@@ -114,7 +101,7 @@
       "type": "command",
       "key": "│ ├󰸌",
       "keyColor": "blue",
-      "text": "theme=$(nomarchy-theme-current); echo -e \"$theme \\e[38m●\\e[37m●\\e[36m●\\e[35m●\\e[34m●\\e[33m●\\e[32m●\\e[31m●\""
+      "text": "theme=$(cat ~/.config/nomarchy/current/theme.name); echo -e \"$theme \\e[38m●\\e[37m●\\e[36m●\\e[35m●\\e[34m●\\e[33m●\\e[32m●\\e[31m●\""
     },
     {
       "type": "terminalfont",
@@ -141,12 +128,6 @@
       "key": "󱫐 Uptime",
       "keyColor": "magenta"
     },
-    {
-      "type": "command",
-      "key": " Update",
-      "keyColor": "magenta",
-      "text": "updated=$(nomarchy-version-pkgs); echo \"$updated\""
-    },
     {
       "type": "custom",
       "format": "\u001b[90m└────────────────────────────────────────────────────┘"