Polish BOS: dark theme, shell QoL, icons, media, clipboard

- Global dark theme: gnome-themes-extra (GTK3 Adwaita-dark), qt5ct/qt6ct
  with Fusion dark skel config, QT_QPA_PLATFORMTHEME=qt5ct env
- Icons/cursor: papirus-icon-theme (Papirus-Dark) + bibata-cursor-theme
  (Bibata-Modern-Ice), set via gsettings autostart + GTK settings.ini + env
- gnome-keyring: credential storage for browsers and apps
- gvfs + gvfs-mtp: nautilus trash, phone access, network shares
- zsh: default user shell (users.conf userShell=/bin/zsh) + skel .zshrc
  with eza/bat/fzf/zoxide aliases, git prompt, fzf history search
- Shell QoL packages: eza, bat, fzf, zoxide
- Media: gst-plugins-good/bad/ugly, pavucontrol
- cliphist: clipboard history daemon (autostart) + SUPER+SHIFT+V bind
- Fonts: noto-fonts-cjk, ttf-jetbrains-mono-nerd

iso/airootfs/etc/skel/.config/qt6ct/qt6ct.conf

@@ -0,0 +1,25 @@
+[Appearance]
+style=Fusion
+color_scheme_path=/usr/share/qt6ct/colors/darker.conf
+custom_palette=true
+standard_dialogs=default
+icon_theme=Papirus-Dark
+
+[Fonts]
+fixed=@Variant(\0\0\0@\0\0\0\x12JetBrains Mono\0\0\0\0\0\0\0\0\0\0\0\0\0\xa0\0\x64\xff\xff\xff\xff)
+general=@Variant(\0\0\0@\0\0\0\x16Noto Sans\0\0\0\0\0\0\0\0\0\0\0\0\x11\0\x64\xff\xff\xff\xff)
+
+[Interface]
+activate_item_on_single_click=1
+buttonbox_layout=0
+cursor_flash_time=1000
+dialog_buttons_have_icons=1
+double_click_interval=400
+gui_effects=@Invalid()
+keyboard_scheme=2
+menus_have_icons=true
+show_shortcuts_in_context_menus=true
+stylesheets=@Invalid()
+toolbutton_style=4
+underline_shortcut=1
+wheel_scroll_lines=3