feat(settings): add theme preference selector replacing header ModeToggle

src/components/settings-panel.tsx

@@ -1,7 +1,9 @@
 "use client";
 
-import { Sparkles, Zap } from "lucide-react";
+import { Monitor, Moon, Sparkles, Sun, Zap } from "lucide-react";
+import { useTheme } from "next-themes";
 import { Badge } from "@/components/ui/badge";
+import { Button } from "@/components/ui/button";
 import { Checkbox } from "@/components/ui/checkbox";
 import { Label } from "@/components/ui/label";
 import { useIsMobile } from "@/hooks/use-mobile";
@@ -26,6 +28,7 @@ export function SettingsPanel({
 	settings,
 }: SettingsPanelProps) {
 	const isMobile = useIsMobile();
+	const { setTheme, theme } = useTheme();
 	const valuePrefix = hasLoadedSettings
 		? "Current preference"
 		: "Default value";
@@ -156,6 +159,55 @@ export function SettingsPanel({
 							</div>
 						</div>
 					</div>
+
+					<div className={settingRowClasses}>
+						<div className="flex items-start gap-3">
+							<div className="mt-0.5 rounded-full bg-primary/10 p-2 text-primary">
+								<Sun className="h-4 w-4" />
+							</div>
+							<div className="min-w-0 flex-1 space-y-3">
+								<div className="space-y-1">
+									<p className="text-sm font-medium text-foreground">
+										Theme preference
+									</p>
+									<p className="text-sm leading-relaxed text-muted-foreground">
+										Choose the appearance LocalCal should use on this device.
+									</p>
+								</div>
+								<div
+									className={cn(
+										"grid gap-2",
+										isMobile ? "grid-cols-1" : "grid-cols-3",
+									)}
+								>
+									<Button
+										type="button"
+										variant={theme === "light" ? "default" : "outline"}
+										onClick={() => setTheme("light")}
+									>
+										<Sun className="h-4 w-4" />
+										Light
+									</Button>
+									<Button
+										type="button"
+										variant={theme === "dark" ? "default" : "outline"}
+										onClick={() => setTheme("dark")}
+									>
+										<Moon className="h-4 w-4" />
+										Dark
+									</Button>
+									<Button
+										type="button"
+										variant={theme === "system" ? "default" : "outline"}
+										onClick={() => setTheme("system")}
+									>
+										<Monitor className="h-4 w-4" />
+										System
+									</Button>
+								</div>
+							</div>
+						</div>
+					</div>
 				</div>
 
 				<div className={cn(settingRowClasses, "space-y-3")}>