Add Helium AppImage and replace Chromium webapps

- Add Helium browser as an AppImage and include it in system packages.
- Rename fluxer package into the appimages module and update imports.
- Add `SUPER+H` keybinding to launch Helium and `SUPER+CONTROL+T` for
  tsukimi.
- Change web‑app desktop entries to use Helium instead of Chromium.
- Disable ungoogled‑chromium and ChatGPT modules on the laptop host.
- Fix a minor typo in a comment within hardware.nix.

hosts/Garand-Desktop/hardware.nix

@@ -58,7 +58,7 @@
     }
   ];
 
-  # Enables DHCP on each ethernet and wireless interface. In case of scripted networking
+  # Enables DHCP on each ethernet and wireless inter.. In case of scripted networking
   # (the default) this is the recommended approach. When using systemd-networkd it's
   # still possible to use this option, but it's recommended to use it in conjunction
   # with explicit per-interface declarations with `networking.interfaces.<interface>.useDHCP`.

hosts/Garand-Laptop/home-modules.nix

@@ -12,7 +12,7 @@ _: {
   Web browsers
   */
   librewolf.enable = true; # Librewolf: a privacy-focused Firefox fork
-  ungoogled-chromium.enable = true; # Ungoogled Chromium: a privacy-focused Chromium fork
+  ungoogled-chromium.enable = false; # Ungoogled Chromium: a privacy-focused Chromium fork
 
   /*
   System utilities
@@ -58,7 +58,7 @@ _: {
       messenger.enable = true; # Messenger: Facebook Messenger
       mastodon.enable = true; # Mastodon: a decentralized social network
       garandcloud.enable = true; # GarandCloud: my Nextcloud instance
-      chatgpt.enable = true; # ChatGPT: a large language model
+      chatgpt.enable = false; # ChatGPT: a large language model
       claude.enable = true; # Claude: a large language model
       glance.enable = true; # Glance: my home server dashboard
       jellyfinClient.enable = true; # Jellyfin: My Jellyfin