Add Opencode and Ollama modules; update configs

Enable Opencode and Ollama in home modules and import their Nix files.
Disable the deprecated system‑module opencode entries and remove it from
the
core packages list.
Add a new GitHub CLI module and a convenient `upf-gh` alias for flake
updates using a GitHub token.
Update the `stylix` configuration to include Opencode styling.
Refresh several flake.lock entries with newer revisions and hashes.

modules/home/default.nix

@@ -19,13 +19,16 @@ _: {
     ./easyeffects.nix
     ./eza.nix
     ./fzf.nix
+    ./gh.nix
     ./git.nix
     ./gtk.nix
     ./kdeConnect.nix
     ./lutris.nix
     ./nextcloud.nix
     ./obs-studio.nix
+    ./ollama.nix
     ./onlyoffice.nix
+    ./opencode.nix
     ./qt.nix
     ./ssh.nix
     ./starship.nix