Fix wallpaper persistence, tray icons, Booru bugs, session launcher

- Persist last-set wallpaper and restore it via exec-once, since
  hyprpaper/mpvpaper start every session with nothing loaded
- Fix Vesktop's system tray icon rendering as a broken texture: only
  resolve tray icons through the icon theme when they're actual names,
  not raw pixmap-sourced image:// URLs
- Launch Hyprland via start-hyprland (its official watchdog launcher)
  instead of the raw binary, removing the startup warning and adding
  hang recovery
- Fix Booru panel: Lewds toggle now actually persists, tag autocomplete
  no longer drops/races overlapping requests, and pagination wraps
  instead of overflowing off-screen
- Remove the redundant gap between windows and sidebars/tiles
  (gaps_in/gaps_out, and duplicate flyout margins stacked on top of
  Hyprland's automatic exclusive-zone inset)

dotfiles/quickshell/RightBar.qml

@@ -76,7 +76,19 @@ PanelWindow {
                 delegate: IconImage {
                     id: trayIcon
                     implicitSize: 18
-                    source: Quickshell.iconPath(modelData.icon, "")
+                    // Only resolve through the icon theme when this is
+                    // actually a themed icon name (e.g. Steam's
+                    // "steam_tray_mono"). Apps that only ever supply a raw
+                    // IconPixmap over the SNI protocol and no IconName at
+                    // all (confirmed via busctl: Vesktop's tray item has no
+                    // IconName property) get an already-usable image:// URL
+                    // back from modelData.icon instead — running that
+                    // through iconPath(), a name/path resolver, mangled it
+                    // into nothing, which is what rendered as a broken-
+                    // texture checkerboard instead of the actual icon.
+                    source: modelData.icon.includes("://")
+                        ? modelData.icon
+                        : Quickshell.iconPath(modelData.icon, "")
                     MouseArea {
                         anchors.fill: parent
                         hoverEnabled: true