Redesign Display Settings, Wallpapers, Booru; add System Monitor, Weather

Display Settings: drag-to-arrange multi-monitor canvas with edge
snapping (locked when only one screen is connected), 8/10-bit depth,
color management presets (sRGB/Wide/EDID/HDR+EDID), SDR
brightness/saturation, ICC profile path, VRR toggle. display-set now
takes a single pre-built descriptor instead of a fixed positional arg
list, since Hyprland's monitor keyword grew well past that.

Wallpapers: fixed the current-wallpaper highlight never loading on
open, added real first-frame thumbnails for animated wallpapers
(wallpaper-thumbs + ffmpeg), bigger 2-column grid, filename filter.

Booru: separate downloads folder from Wallpapers so browsing doesn't
clutter the wallpaper picker, bigger grid, Safe/Moderate/Explicit
rating tiers replacing the old binary toggle, sort order (Newest/
Score/Random). Fixed pagination being completely broken (a Flow
anchor violation was silently disabling the whole layout) and
Danbooru's Random sort (order:random tag times out server-side --
switched to their random=true endpoint for that case).

Wi-Fi panel: added a "Scanning.../No networks found" state and a
manual rescan button -- previously showed nothing either way, making
"still scanning" indistinguishable from a real failure.

Bluetooth: auto-scans on open like Wi-Fi now, instead of requiring a
manual click every time.

New: System Monitor panel (CPU/RAM/GPU/VRAM/disk usage, NVIDIA or AMD
detected automatically) and Weather panel (IP-geolocated or a typed
city, current + hourly forecast, Open-Meteo, no API key) with a
compact taskbar badge.

dotfiles/quickshell/Meter.qml

@@ -0,0 +1,26 @@
+import QtQuick
+
+// Read-only horizontal usage bar — CPU/RAM/GPU/VRAM/disk meters in the
+// System Monitor panel all need the same "filled fraction of a track"
+// visual, just with a different value/color each time.
+Item {
+    id: root
+    property real value: 0 // 0..1
+    property color barColor: Theme.accent
+    implicitHeight: 8
+
+    Rectangle {
+        anchors.fill: parent
+        color: Theme.bgAlt
+        border.width: 1
+        border.color: Theme.borderDim
+    }
+    Rectangle {
+        anchors.left: parent.left
+        anchors.top: parent.top
+        anchors.bottom: parent.bottom
+        anchors.margins: 1
+        width: Math.max(0, (parent.width - 2) * Math.min(1, Math.max(0, root.value)))
+        color: root.barColor
+    }
+}