Make flake self-contained - consolidate installer-replication

BREAKING CHANGE: Remove external dots-hyprland dependency

- Imported all essential configs from dots-hyprland/installer-replication
- Added complete configs/ directory with:
  - hypr/ - Hyprland configuration
  - quickshell/ - Quickshell widgets and config
  - applications/ - Application configurations
  - scripts/ - Utility scripts
  - matugen/ - Material You theming
- Updated flake.nix to use local ./configs instead of external repo
- Simplified update-flake script (removed external repo management)
- Updated README to reflect self-contained architecture
- All builds pass with local configurations

Benefits:
- No external repository dependencies
- Faster builds (no network dependencies)
- Version controlled configs in single repo
- Easier maintenance and development
- Complete installer replication in one place

configs/quickshell/modules/common/widgets/StyledRectangularShadow.qml

@@ -0,0 +1,14 @@
+import QtQuick
+import QtQuick.Effects
+import qs.modules.common
+
+RectangularShadow {
+    required property var target
+    anchors.fill: target
+    radius: target.radius
+    blur: 0.9 * Appearance.sizes.elevationMargin
+    offset: Qt.vector2d(0.0, 1.0)
+    spread: 1
+    color: Appearance.colors.colShadow
+    cached: true
+}