Implement volume control for boxy via Home Assistant

Add remote volume control for the living room media center (boxy) that
controls the Denon AVR through Home Assistant instead of local audio.

- Create plasma-manager-kodi role with custom KDE hotkeys for volume
  up/down/mute that execute shell scripts
- Scripts retrieve HA token from KDE Wallet and send API requests to
  control media_player.denon_avr_s970h_2
- Add retry logic (3 attempts) and error notifications
- Enable KDE Wallet PAM integration for automatic wallet unlock
- Configure KDE settings: Breeze Dark theme, disable screen locking,
  empty session restore
- Add kconfig package for debugging tools

home/home-kodi.nix

@@ -0,0 +1,28 @@
+{ pkgs, globalInputs, system, ... }:
+
+{
+  # Home Manager configuration for kodi user on boxy
+  # Focused on media center volume control via Home Assistant
+
+  home.username = "kodi";
+  home.homeDirectory = "/home/kodi";
+  home.stateVersion = "24.05";
+
+  # Enable minimal roles for kodi user
+  home.roles = {
+    base.enable = true;
+    plasma-manager-kodi.enable = true;
+  };
+
+  home.packages = with pkgs; [
+    kdePackages.kconfig
+  ];
+
+  targets.genericLinux.enable = true;
+  home.sessionVariables = {};
+  home.sessionPath = [];
+
+  imports = [
+    ./roles
+  ];
+}