Switch desktop environment from Hyprland to Budgie; app/audio overhaul

Hyprland problems prompted a full switch to Budgie (X11, lightdm).
Removes every Hyprland/Quickshell dotfile, theming script, and
hypr-specific module (theme.nix, the whole scripts/ theming pipeline,
hyprland.conf/hyprpaper.conf, the Quickshell shell QML, kitty/mako/
rofi configs) in favor of Budgie's own panel/session/theming and a
GSettings-driven icon/cursor override.

App changes:
- Konsole/Dolphin replace kitty/Thunar as the default terminal and
  file manager; dropped xterm too (services.xserver.excludePackages)
- Added Okular (PDF/document viewer), KCalc (calculator), Elisa
  (audio player) -- nothing filled those roles before
- Added OBS Studio

Audio/voice:
- EasyEffects for real-time mic/output effects (creates its own
  selectable "Easy Effects Source" virtual mic automatically)
- A standalone "Virtual Microphone" PipeWire device (loopback module,
  services.pipewire.extraConfig), fully independent of the real mic,
  for routing EasyEffects/Soundux output separately from what Discord
  etc. use by default
- qpwgraph for manual patchbay routing into the above
- Soundux (soundboard) installed via Flatpak -- no longer packaged in
  this nixpkgs channel

default-apps.nix: Okular wired into mimeapps.list alongside the
existing Gwenview/Ark defaults; removed the Thunar-specific
"Open Terminal Here" custom-action tmpfiles rule (dead now that
Thunar's gone -- Dolphin gets the same via its built-in konsolepart
terminal panel for free).

modules/desktop.nix

@@ -1,101 +1,41 @@
 { config, pkgs, ... }:
 
 {
-  # --- Hyprland: Wayland compositor ---
-  programs.hyprland = {
-    enable = true;
-    xwayland.enable = true;
-  };
-
-  # --- greetd + tuigreet: minimal TUI login manager, launches Hyprland directly ---
-  services.greetd = {
-    enable = true;
-    settings.default_session = {
-      # start-hyprland, not the raw Hyprland binary: it's Hyprland's own
-      # watchdog-wrapped launcher (ships alongside Hyprland in the same
-      # package) that also auto-restarts the compositor if it hangs.
-      # Launching the raw binary directly works but logs a startup warning
-      # ("Hyprland is being launched without start-hyprland. This is highly
-      # advised against.") and skips that recovery.
-      command = "${pkgs.tuigreet}/bin/tuigreet --time --remember --remember-session --cmd start-hyprland";
-      user = "greeter";
-    };
-  };
-
-  # --- XDG portals: screen share, file pickers, etc. ---
-  xdg.portal = {
-    enable = true;
-    extraPortals = [ pkgs.xdg-desktop-portal-hyprland pkgs.xdg-desktop-portal-gtk ];
-    config.common.default = [ "hyprland" "gtk" ];
-  };
+  # --- Budgie: X11 desktop environment, lightdm login manager ---
+  services.xserver.enable = true;
+  services.xserver.displayManager.lightdm.enable = true;
+  services.desktopManager.budgie.enable = true;
 
   security.polkit.enable = true;
 
-  # Keyboard layout for console/XWayland/greetd; Hyprland's own input block
-  # in hyprland/hyprland.conf mirrors this.
+  # Keyboard layout for console/X11/lightdm
   services.xserver.xkb = {
     layout = "pl";
     variant = "";
   };
 
-  # Thunar: thumbnails, trash/volume mount integration, settings storage
+  # Thumbnails + trash/volume mount integration for Dolphin and Budgie's
+  # default Nemo file manager alike.
   services.tumbler.enable = true;
   services.gvfs.enable = true;
-  programs.xfconf.enable = true;
 
-  # Native Wayland backend for Electron/Chromium-based apps
-  environment.sessionVariables.NIXOS_OZONE_WL = "1";
+  # Drop the xterm fallback terminal xserver.nix installs unconditionally —
+  # Konsole is the real terminal here.
+  services.xserver.excludePackages = [ pkgs.xterm ];
 
-  # --- Dotfiles: symlink tracked configs into the user's home ---
-  # Editing /etc/nixos/hyprland or /etc/nixos/dotfiles takes effect on the
-  # next reload of the respective app (no rebuild needed for config-only
-  # tweaks; a rebuild re-runs the symlink if the target path itself changes).
-  systemd.tmpfiles.rules = [
-    "d /home/nexoniarz/.config/hypr 0755 nexoniarz users -"
-    "L+ /home/nexoniarz/.config/hypr/hyprland.conf - - - - /etc/nixos/hyprland/hyprland.conf"
-    "L+ /home/nexoniarz/.config/hypr/hyprpaper.conf - - - - /etc/nixos/hyprland/hyprpaper.conf"
-
-    "d /home/nexoniarz/.config/kitty 0755 nexoniarz users -"
-    "L+ /home/nexoniarz/.config/kitty/kitty.conf - - - - /etc/nixos/dotfiles/kitty/kitty.conf"
-    # Colors set live via the Quickshell Theme picker — see kitty.conf's
-    # `include theme.conf`. Empty by default; kitty-theme-set writes to it.
-    "f /home/nexoniarz/.config/kitty/theme.conf 0644 nexoniarz users - -"
-
-    "d /home/nexoniarz/.config/rofi 0755 nexoniarz users -"
-    "L+ /home/nexoniarz/.config/rofi/config.rasi - - - - /etc/nixos/dotfiles/rofi/config.rasi"
-    # Colors set live via the Quickshell Theme picker — see config.rasi's
-    # `@import "theme.rasi"`. Empty by default; rofi-theme-set writes to it.
-    "f /home/nexoniarz/.config/rofi/theme.rasi 0644 nexoniarz users - -"
-
-    "d /home/nexoniarz/.config/mako 0755 nexoniarz users -"
-    "L+ /home/nexoniarz/.config/mako/config - - - - /etc/nixos/dotfiles/mako/config"
-
-    # Quickshell is multi-file with relative imports, so the whole directory
-    # is symlinked rather than a single file.
-    "L+ /home/nexoniarz/.config/quickshell - - - - /etc/nixos/dotfiles/quickshell"
-
-    # $HOME/Wallpapers, not $HOME/Pictures/Wallpapers — this system's locale
-    # (pl_PL) means the real XDG Pictures dir is ~/Obrazy, not ~/Pictures.
-    # Living directly under $HOME sidesteps that entirely.
-    "d /home/nexoniarz/Wallpapers 0755 nexoniarz users -"
-    "d /home/nexoniarz/Screenshots 0755 nexoniarz users -"
-
-    # User-editable cursor theme choice (set live via the Quickshell cursor
-    # picker) — created empty if missing, never overwritten if it already
-    # has content, since it's runtime state rather than tracked config.
-    "f /home/nexoniarz/.config/hypr/cursor.conf 0644 nexoniarz users - -"
-
-    # Same deal for display settings (mode/scale/transform per monitor,
-    # set via the Quickshell display picker) — without this file backing
-    # them, they only ever applied live via hyprctl and got silently
-    # reset by hyprland.conf's generic fallback monitor rule any time
-    # Hyprland re-evaluated monitor state.
-    "f /home/nexoniarz/.config/hypr/display.conf 0644 nexoniarz users - -"
-
-    # Same deal for window border colors (accent/border, set live via the
-    # Quickshell Theme picker) — without this file, they only ever applied
-    # via hyprctl and would fall back to hyprland.conf's own general{}
-    # defaults any time Hyprland re-evaluated its config.
-    "f /home/nexoniarz/.config/hypr/theme.conf 0644 nexoniarz users - -"
+  # GTK/Qt themselves stay at their stock defaults (no forced dark mode, no
+  # custom CSS) — only the icon and cursor theme are picked explicitly, via
+  # Budgie's own GSettings-override hook rather than a custom script.
+  # (extraGSettingsOverridePackages is for packages that ship their own
+  # gsettings-schema overrides, e.g. plugins — not theme packages, which
+  # just need to be on the system path for their icons/cursors to resolve.)
+  environment.systemPackages = [
+    pkgs.gruvbox-plus-icons
+    pkgs.bibata-cursors
   ];
+  services.desktopManager.budgie.extraGSettingsOverrides = ''
+    [org.gnome.desktop.interface]
+    icon-theme='Gruvbox-Plus-Dark'
+    cursor-theme='Bibata-Modern-Classic'
+  '';
 }