chore(branding): update fastfetch ASCII icon and fix branding typos

- Optimized assets/branding/icon.txt with multi-color placeholders for fastfetch.
- Updated config/fastfetch/config.jsonc to use the new multi-colored icon.
- Added icon and svg branding assets to modules/home/theme-files.nix.
- Fixed 'Nnomarchy' typo to 'Nomarchy' and updated branding paths in several scripts.
- Corrected screensaver and welcome scripts to use the centralized branding assets.

config/fastfetch/config.jsonc

@@ -2,8 +2,8 @@
   "$schema": "https://github.com/fastfetch-cli/fastfetch/raw/dev/doc/json_schema.json",
   "logo": {
     "type": "file",
-    "source": "~/.config/nomarchy/branding/logo.txt",
-    "color": { "1": "green" },
+    "source": "~/.config/nomarchy/branding/icon.txt",
+    "color": { "1": "green", "2": "blue" },
     "padding": {
       "top": 2,
       "right": 6,