fix(theme): set default to summer-night and fix scripts on live ISO

- Update lib/state-schema.nix to default both home and system themes to 'summer-night'.
- Fix 'nomarchy-theme-list' and 'nomarchy-theme-set-templates' to resolve themes and templates from '~/.local/share/nomarchy' instead of the obsolete '$NOMARCHY_PATH' (fixing failures on Live ISO).
- Update 'nomarchy-welcome' to properly convert Title Case theme display names back to kebab-case identifiers and add input validation to prevent crashes.
- Fix installer impermanence symlink by using a relative path ('../persist/etc/nixos'), ensuring it resolves during 'nixos-install' both inside and outside the chroot.
- Deploy '~/.XCompose' symlink via Home Manager and add 'nomarchy-restart-xcompose' to the menu.
- Relocate 'Nomarchy.ttf' to 'core/branding/' and move user-level scripts ('pkg-add', 'pkg-remove', 'env-update', 'preflight-migration') to 'features/scripts/utils/' to align with the distro architecture.
- Remove obsolete '$NOMARCHY_PATH' exports and redundant 'bashrc' template.
- Export theme templates via 'xdg.dataFile' for script accessibility.

themes/engine/scripts/nomarchy-theme-list

@@ -2,8 +2,8 @@
 set -e
 
 {
-  find ~/.config/nomarchy/themes/ -mindepth 1 -maxdepth 1 \( -type d -o -type l \) -printf '%f\n'
-  find "$NOMARCHY_PATH/themes/palettes/" -mindepth 1 -maxdepth 1 -type d -printf '%f\n'
+  find ~/.config/nomarchy/themes/ -mindepth 1 -maxdepth 1 \( -type d -o -type l \) -printf '%f\n' 2>/dev/null || true
+  find ~/.local/share/nomarchy/themes/ -mindepth 1 -maxdepth 1 -type d -printf '%f\n' 2>/dev/null || true
 } | sort -u | while read -r name; do
   echo "$name" | sed -E 's/(^|-)([a-z])/\1\u\2/g; s/-/ /g'
 done

themes/engine/scripts/nomarchy-theme-set-templates

@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-TEMPLATES_DIR="$NOMARCHY_PATH/themes/templates"
+TEMPLATES_DIR="$HOME/.local/share/nomarchy/templates"
 USER_TEMPLATES_DIR="$HOME/.config/nomarchy/themes/templates"
 NEXT_THEME_DIR="$HOME/.config/nomarchy/current/theme"
 COLORS_FILE="$NEXT_THEME_DIR/colors.toml"