Add Noctalia shell with Quickshell overview

- Add `noctalia` input to flake and lock it in `flake.lock`.
- Include `noctalia` and `quickshell` modules in `flake.nix`.
- Extend core packages to accept `inputs` and `system`; add
  `quickshell.nix`
  with required Qt6 packages and environment variables.
- Enable `upower` service for battery handling.
- Add home modules `noctalia.nix` and `overview.nix` (QML UI, README,
  assets, widgets, services) to provide a workspace overview.
- Comment out unused rofi and web‑search binds; update `exec‑once` to
  start
  the overview daemon and `noctalia-shell`.
- Provide `restart.noctalia` script and its Nix wrapper.
- Enable `noctalia-shell` in `stylix` configuration.

modules/home/noctalia.nix

@@ -0,0 +1,28 @@
+{
+  pkgs,
+  inputs,
+  system,
+  lib,
+  ...
+}: let
+  noctalia = inputs.noctalia.packages.${system}.default;
+  configDir = "${noctalia}/share/noctalia-shell";
+in {
+  home = {
+    packages = with pkgs; [
+      noctalia
+      quickshell # Ensure quickshell is available for the service
+    ];
+    activation.seedNoctaliaShellCode = lib.hm.dag.entryAfter ["writeBoundary"] ''
+      set -eu
+      DEST="$HOME/.config/quickshell/noctalia-shell"
+      SRC="${configDir}"
+
+      if [ ! -d "$DEST" ]; then
+        $DRY_RUN_CMD mkdir -p "$HOME/.config/quickshell"
+        $DRY_RUN_CMD cp -R "$SRC" "$DEST"
+        $DRY_RUN_CMD chmod -R u+rwX "$DEST"
+      fi
+    '';
+  };
+}