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

features/apps/alacritty/default.nix

@@ -0,0 +1,26 @@
+{ config, pkgs, lib, ... }:
+
+{
+  programs.alacritty = {
+    enable = lib.mkDefault true;
+    settings = lib.mkDefault {
+      env = {
+        TERM = "xterm-256color";
+      };
+      terminal = {
+        osc52 = "CopyPaste";
+      };
+      window = {
+        padding = { x = 14; y = 14; };
+        decorations = "None";
+      };
+      keyboard = {
+        bindings = [
+          { key = "Insert"; mods = "Shift"; action = "Paste"; }
+          { key = "Insert"; mods = "Control"; action = "Copy"; }
+          { key = "Return"; mods = "Shift"; chars = "\\u001B\\r"; }
+        ];
+      };
+    };
+  };
+}