refactor: implement component-based architecture for enhanced maintainability

- Reorganize directory structure into core/, features/, and themes/
- Colocate application Nix logic, configs, scripts, and theme overrides
- Implement 'Inversion of Control' for theming: apps now pull theme-specific layouts
- Update flake.nix and shared library paths to match the new structure
- Document the new Feature-Centric architecture in README.md

themes/templates/kitty.conf.tpl

@@ -0,0 +1,27 @@
+foreground {{ foreground }}
+background {{ background }}
+selection_foreground {{ selection_foreground }}
+selection_background {{ selection_background }}
+
+cursor {{ cursor }}
+cursor_text_color {{ background }}
+
+active_border_color {{ accent }}
+active_tab_background {{ accent }}
+
+color0 {{ color0 }}
+color1 {{ color1 }}
+color2 {{ color2 }}
+color3 {{ color3 }}
+color4 {{ color4 }}
+color5 {{ color5 }}
+color6 {{ color6 }}
+color7 {{ color7 }}
+color8 {{ color8 }}
+color9 {{ color9 }}
+color10 {{ color10 }}
+color11 {{ color11 }}
+color12 {{ color12 }}
+color13 {{ color13 }}
+color14 {{ color14 }}
+color15 {{ color15 }}