Add modular interactive widgets to the Quickshell bar

Introduces a widgets/ directory of first-party QML modules and a common/
helpers library. Widgets auto-load by name from
default/quickshell/bar/widgets/<name>.qml — no edits to shell.qml needed
for additions beyond the firstPartyWidgets registry.

New widgets (all orientation-aware, top/bottom/left/right):
- media: MPRIS now-playing with scrolling label, cover art popup,
  play/pause/skip controls
- audioPanel: master volume slider, output device picker, per-app mixer
- networkPanel: Wi-Fi scan + connect, current connection details
- bluetoothPanel: paired device list, connect/disconnect, battery
- calendar: month grid popup keyed to today
- notificationCenter: live notification feed, DND toggle, clear all
- brightness: slider popup with scroll-to-adjust
- powerProfile: power-saver/balanced/performance picker (UPower)
- systemStats: inline CPU + RAM sparklines, expanded popup with btop
- weatherFlyout: weather popup with refresh and full report
- workspacesPro: animated focus indicator that slides between workspaces
- powerMenu: lock/suspend/log out/reboot/shutdown popup
- idleInhibitor: coffee-cup toggle wired to omarchy-toggle-idle
- microphone: mic state + mute toggle + scroll volume

Common helpers (default/quickshell/bar/common/):
- WidgetButton: hover/press scale animation, tooltip integration
- PopupCard: orientation-aware anchor + slide-in opacity transition
- Slider: drag/wheel-able linear slider with knob hover bump
- PillButton: rounded action button with icon + label

Bar root gains requestPopout/releasePopout so only one popup is open at
a time across widgets.

Updates bar-defaults.json to ship the new widgets out of the box while
keeping the legacy modules available.

default/quickshell/bar/shell.qml

@@ -64,6 +64,17 @@ ShellRoot {
   property var tooltipTarget: null
   property string tooltipText: ""
   property bool tooltipShown: false
+  property var activePopout: null
+
+  function requestPopout(owner) {
+    if (activePopout === owner) return
+    if (activePopout && "closePopout" in activePopout) activePopout.closePopout()
+    activePopout = owner
+  }
+
+  function releasePopout(owner) {
+    if (activePopout === owner) activePopout = null
+  }
 
   readonly property bool vertical: position === "left" || position === "right"
   readonly property int barSize: vertical ? 28 : 26
@@ -248,6 +259,28 @@ ShellRoot {
     return source ? fileUrl(source) : ""
   }
 
+  readonly property var firstPartyWidgets: ({
+    "media": true,
+    "audioPanel": true,
+    "networkPanel": true,
+    "bluetoothPanel": true,
+    "calendar": true,
+    "notificationCenter": true,
+    "brightness": true,
+    "powerProfile": true,
+    "systemStats": true,
+    "weatherFlyout": true,
+    "workspacesPro": true,
+    "powerMenu": true,
+    "idleInhibitor": true,
+    "microphone": true
+  })
+
+  function firstPartyWidgetSource(name) {
+    if (!firstPartyWidgets[String(name)]) return ""
+    return fileUrl(omarchyPath + "/default/quickshell/bar/widgets/" + String(name) + ".qml")
+  }
+
   function networkCommand() {
     return [
       "route_device=$(ip route get 1.1.1.1 2>/dev/null | awk '{ for (i = 1; i <= NF; i++) if ($i == \"dev\") { print $(i + 1); exit } }')",
@@ -1048,9 +1081,11 @@ ShellRoot {
     required property string moduleName
     readonly property string customType: root.customModuleType(moduleName)
     readonly property var builtinComponent: customType ? null : root.builtinModuleComponent(moduleName)
+    readonly property string firstPartySource: customType || builtinComponent ? "" : root.firstPartyWidgetSource(moduleName)
     readonly property bool qmlCustom: customType === "qml"
     readonly property bool commandCustom: customType === "command"
-    readonly property var activeItem: qmlCustom ? qmlLoader.item : componentLoader.item
+    readonly property bool firstParty: firstPartySource !== ""
+    readonly property var activeItem: qmlCustom || firstParty ? qmlLoader.item : componentLoader.item
 
     implicitWidth: activeItem && activeItem.visible ? activeItem.implicitWidth : 0
     implicitHeight: activeItem && activeItem.visible ? activeItem.implicitHeight : 0
@@ -1059,15 +1094,15 @@ ShellRoot {
 
     Loader {
       id: componentLoader
-      active: !slot.qmlCustom
+      active: !slot.qmlCustom && !slot.firstParty
       sourceComponent: slot.builtinComponent || (slot.commandCustom ? customCommandModuleComponent : emptyModuleComponent)
       anchors.fill: parent
     }
 
     Loader {
       id: qmlLoader
-      active: slot.qmlCustom
-      source: slot.qmlCustom ? root.customModuleSource(slot.moduleName) : ""
+      active: slot.qmlCustom || slot.firstParty
+      source: slot.qmlCustom ? root.customModuleSource(slot.moduleName) : (slot.firstParty ? slot.firstPartySource : "")
       anchors.fill: parent
       onLoaded: {
         if (item && "bar" in item) item.bar = root