feat: fade-in animation, PKGBUILD for system installation

- CSS opacity transition (350ms ease-in) for panel and wallpaper
- PKGBUILD for makepkg/pacman installation
- .gitignore for makepkg build artifacts

src/moonset/panel.py

@@ -107,6 +107,12 @@ class WallpaperWindow(Gtk.ApplicationWindow):
         background.set_vexpand(True)
         self.set_child(background)
 
+        self.connect("map", self._on_map)
+
+    def _on_map(self, widget: Gtk.Widget) -> None:
+        """Trigger fade-in once the window is visible."""
+        GLib.idle_add(lambda: self.add_css_class("visible") or GLib.SOURCE_REMOVE)
+
 
 class PanelWindow(Gtk.ApplicationWindow):
     """Fullscreen power menu window for the primary monitor."""
@@ -242,10 +248,14 @@ class PanelWindow(Gtk.ApplicationWindow):
         self.add_controller(controller)
 
     def _on_map(self, widget: Gtk.Widget) -> None:
-        """Grab focus on the first action button once the window is visible."""
-        # Delay focus grab — layer shell keyboard interactivity may not
-        # be ready at map time
+        """Trigger fade-in and grab focus once the window is visible."""
+        GLib.idle_add(self._fade_in)
+
+    def _fade_in(self) -> bool:
+        """Add visible class to trigger CSS opacity transition, then grab focus."""
+        self.add_css_class("visible")
         GLib.idle_add(self._grab_initial_focus)
+        return GLib.SOURCE_REMOVE
 
     def _grab_initial_focus(self) -> bool:
         """Set focus on the first action button."""

src/moonset/style.css

@@ -6,11 +6,23 @@ window.panel {
     background-color: @theme_bg_color;
     background-size: cover;
     background-position: center;
+    opacity: 0;
+    transition: opacity 350ms ease-in;
+}
+
+window.panel.visible {
+    opacity: 1;
 }
 
 /* Wallpaper-only window for secondary monitors */
 window.wallpaper {
     background-color: @theme_bg_color;
+    opacity: 0;
+    transition: opacity 350ms ease-in;
+}
+
+window.wallpaper.visible {
+    opacity: 1;
 }
 
 /* Round avatar image */