feat(ui): PowerUse-Einstellungen nach Settings -> Ausfuehrung verschieben

Schalter, Zeitfenster und Handoff-Prozent lagen im Usage-Monitor und mussten
in SettingsModalViewModel nur load->save durchgeschleift werden, damit ein
Settings-Speichern sie nicht zurueckwirft. Jetzt gehoeren sie dem General-Tab,
der Monitor ist wieder nur Anzeige + Threshold-Drag, und "Jetzt aktualisieren"
sitzt als Icon in der Titelleiste (neuer ModalShell.HeaderActions-Slot).

src/ClaudeDo.Data/Wire.cs

@@ -37,13 +37,12 @@ public record AppSettingsDto(
     int UsageThrottleSevenDaySoftPct = 50,
     int UsageThrottleSevenDayHardPct = 65,
     bool AutoContinueOnUsageLimit = false,
-    // PowerUse master switch — toggled on the usage monitor, not typed in Settings. Only takes
-    // effect for a list that also set PowerUseAllowed.
+    // PowerUse master switch — Settings → Execution. Only takes effect for a list that also set
+    // PowerUseAllowed.
     bool PowerUseEnabled = false,
     int ListHandlerMaxHandoffs = 4,
     // PowerUse time window (`HH:mm`, local, null = round the clock) + the 5h-usage percentage at
-    // which a PowerUse handler session should hand off. Also usage-monitor-owned, so Settings has
-    // to round-trip them too.
+    // which a PowerUse handler session should hand off. Same Settings tab.
     string? PowerUseWindowStart = null,
     string? PowerUseWindowEnd = null,
     int PowerUseHandoffPct = 95);