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

core/system/systemd.nix

@@ -0,0 +1,64 @@
+{ config, pkgs, lib, ... }:
+
+{
+  systemd.settings.Manager.DefaultTimeoutStopSec = lib.mkDefault "5s";
+
+  systemd.services."user@".serviceConfig.TimeoutStopSec = lib.mkDefault "5s";
+
+  powerManagement.powerDownCommands = ''
+    # --- force-igpu ---
+    # Use the Vfio to Integrated trick to turn off NVIDIA dgpu when in integrated mode
+    if [[ $1 == "hibernate" ]] && ${pkgs.coreutils}/bin/lsmod | grep -q supergfxd; then
+      ${pkgs.supergfxctl}/bin/supergfxctl -m Vfio || true
+      sleep 1
+    fi
+
+    # --- keyboard-backlight ---
+    # Turn off keyboard backlight before hibernate to prevent hang on power-off.
+    if [[ $1 == "hibernate" ]]; then
+      device=""
+      for candidate in /sys/class/leds/*kbd_backlight*; do
+        if [[ -e "$candidate" ]]; then
+          device="$(${pkgs.coreutils}/bin/basename "$candidate")"
+          break
+        fi
+      done
+      if [[ -n "$device" ]]; then
+        ${pkgs.brightnessctl}/bin/brightnessctl -d "$device" set 0 >/dev/null 2>&1 || true
+      fi
+    fi
+
+    # --- unmount-fuse ---
+    # Lazy-unmount gvfsd-fuse filesystems before suspend/hibernate
+    while IFS=' ' read -r _ mountpoint fstype _; do
+      if [[ $fstype == fuse.gvfsd-fuse ]]; then
+        mountpoint=$(printf '%b' "$mountpoint")
+        ${pkgs.fuse3}/bin/fusermount3 -uz "$mountpoint" 2>/dev/null || ${pkgs.fuse}/bin/fusermount -uz "$mountpoint" 2>/dev/null || true
+      fi
+    done < /proc/mounts
+  '';
+
+  powerManagement.resumeCommands = ''
+    # --- force-igpu ---
+    if ${pkgs.coreutils}/bin/lsmod | grep -q supergfxd; then
+      sleep 4
+      ${pkgs.supergfxctl}/bin/supergfxctl -m Vfio || true
+      sleep 1
+      ${pkgs.supergfxctl}/bin/supergfxctl -m Integrated || true
+    fi
+
+    # --- unmount-fuse ---
+    (
+      sleep 5
+      for uid_dir in /run/user/*; do
+        uid="$(${pkgs.coreutils}/bin/basename "$uid_dir")"
+        if [[ -S $uid_dir/bus ]]; then
+          sudo -u "#$uid" env \
+            DBUS_SESSION_BUS_ADDRESS="unix:path=$uid_dir/bus" \
+            XDG_RUNTIME_DIR="$uid_dir" \
+            systemctl --user restart gvfs-daemon.service 2>/dev/null || true
+        fi
+      done
+    ) &
+  '';
+}