Spawn shell subprocesses with bash -c instead of bash -lc

Each `bash -lc` starts a login shell that re-sources the profile
(mise activation, /etc/profile.d) on every invocation — ~16 forks per
call versus ~2 for `bash -c` — which taxes every menu/panel/launcher
action the shell shells out for. The session already exports PATH and
env to the shell, so omarchy commands resolve fine under `bash -c`.

Switch the internal/omarchy-owned spawns (theme+background switches,
brightness, monitor scaling, DNS, lock/fingerprint, keyboard-layout
probe, voxtype status, and the `:`/printf state-file writes) to
`bash -c`. Leave `bash -lc` on the sites that run user-configurable
commands (custom bar-widget exec, menu provider/guard scripts,
launcher scan commands, configurable idle/screensaver command), where
a user's command may rely on their login environment.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

shell/plugins/panels/monitor/Panel.qml

@@ -213,7 +213,7 @@ Panel {
     }
 
     root.brightnessSetQueued = false
-    setBrightnessProc.command = ["bash", "-lc", "omarchy-brightness-display --no-osd " + percent + "%"]
+    setBrightnessProc.command = ["bash", "-c", "omarchy-brightness-display --no-osd " + percent + "%"]
     setBrightnessProc.running = true
   }
 
@@ -248,7 +248,7 @@ Panel {
   }
 
   function setScale(scale) {
-    actionProc.command = ["bash", "-lc", "omarchy-hyprland-monitor-scaling " + scale]
+    actionProc.command = ["bash", "-c", "omarchy-hyprland-monitor-scaling " + scale]
     if (!actionProc.running) actionProc.running = true
   }