Add visual bar customizer

Each layout entry is now an object — {id, ...inline settings} — instead
of a (name, separate modules map) pair. Multiple instances of the same
widget are trivially supported (spacer is the main beneficiary). Settings
travel with the entry, so reordering keeps them attached.

shell.qml:
- normalizeLayout converts string entries to {id} and drops invalid ones
- ModuleSlot binds to a full entry; moduleName and moduleSettings derive
  from it via entryId/entrySettings helpers
- centerAnchor lookup walks layoutEntries directly
- builtinBarConfig defaults use the object form
- README + bar-defaults.json updated to the new schema

bar-settings/ (new Quickshell config):
- Top toolbar with Reset / Save and Position / centerAnchor dropdowns
- Three section editors (left/center/right) with current widgets shown
  as cards: name + description + move up/down/settings/remove buttons
- '+ Add widget' menu per section, sorted alphabetically by display name
  (only spacer can repeat; everything else is one per bar)
- Per-widget settings dialog (FloatingWindow) loads an inline schema for
  widgets in the catalog. Initial schemas: spacer (size), calendar
  (formats), brightness (step)
- FileView { atomicWrites } writes to ~/.config/omarchy/bar.json on Save

omarchy-launch-bar-settings + hypr window rules pin the settings window
to a 760px floating square. controlCenter gains a 'Customize bar…' button
that launches it.

default/quickshell/bar/bar-defaults.json

@@ -3,20 +3,34 @@
   "fontFamily": "JetBrainsMono Nerd Font",
   "centerAnchor": "calendar",
   "layout": {
-    "left": ["omarchy", "workspacesPro", "activeWindow"],
-    "center": ["media", "calendar", "weatherFlyout", "update", "voxtype", "screenRecording", "idle", "notifications"],
-    "right": ["tray", "systemStats", "microphone", "bluetoothPanel", "networkPanel", "audioPanel", "nightLight", "brightness", "powerProfile", "battery", "controlCenter", "powerMenu"]
-  },
-  "modules": {
-    "calendar": {
-      "format": "dddd HH:mm",
-      "formatAlt": "dd MMMM 'W'ww yyyy",
-      "verticalFormat": "HH\n—\nmm"
-    },
-    "clock": {
-      "format": "dddd HH:mm",
-      "formatAlt": "dd MMMM 'W'ww yyyy",
-      "verticalFormat": "HH\n—\nmm"
-    }
+    "left": [
+      { "id": "omarchy" },
+      { "id": "workspacesPro" },
+      { "id": "activeWindow" }
+    ],
+    "center": [
+      { "id": "media" },
+      { "id": "calendar", "format": "dddd HH:mm", "formatAlt": "dd MMMM 'W'ww yyyy", "verticalFormat": "HH\n—\nmm" },
+      { "id": "weatherFlyout" },
+      { "id": "update" },
+      { "id": "voxtype" },
+      { "id": "screenRecording" },
+      { "id": "idle" },
+      { "id": "notifications" }
+    ],
+    "right": [
+      { "id": "tray" },
+      { "id": "systemStats" },
+      { "id": "microphone" },
+      { "id": "bluetoothPanel" },
+      { "id": "networkPanel" },
+      { "id": "audioPanel" },
+      { "id": "nightLight" },
+      { "id": "brightness" },
+      { "id": "powerProfile" },
+      { "id": "battery" },
+      { "id": "controlCenter" },
+      { "id": "powerMenu" }
+    ]
   }
 }