Migrate bos-settings from GTK4 to Tauri + Svelte 5

Ports every remaining view (Keybinds, the last one — dual Flat/MultiLayout
schema detection, per-action dedicated fields with a raw-JSON fallback for
anything not modeled) and removes the now-fully-dead GTK4 crate (root
Cargo.toml + src/), leaving src-tauri/ as the single Rust binary crate.

Also folds in the UX pass done alongside the migration: responsive
multi-column layout instead of a single centered column, chip/dropdown
pickers replacing free-typed fields (Wi-Fi networks, Bar style, keyboard
layout, tag lists), consistent pill-switch toggles and boxed-list card
styling across every page, and a sidebar scroll-chaining fix.

frontend/src/lib/views/Power.svelte

@@ -0,0 +1,105 @@
+<script lang="ts">
+	import { onMount } from "svelte";
+	import { invoke } from "@tauri-apps/api/core";
+	import ViewScaffold from "$lib/components/ViewScaffold.svelte";
+	import InfoRow from "$lib/components/InfoRow.svelte";
+	import Row from "$lib/components/Row.svelte";
+	import Group from "$lib/components/Group.svelte";
+	import Hint from "$lib/components/Hint.svelte";
+
+	interface PowerInfo {
+		battery: [string, string][];
+		power_source: string;
+		brightness_pct: number | null;
+		charge_start: number | null;
+		charge_end: number | null;
+		tlp_profile: string | null;
+	}
+
+	let info = $state<PowerInfo | null>(null);
+	let brightness = $state(0);
+	let chargeStart = $state(0);
+	let chargeEnd = $state(100);
+
+	onMount(async () => {
+		info = await invoke<PowerInfo>("get_power_info");
+		brightness = info.brightness_pct ?? 0;
+		chargeStart = info.charge_start ?? 0;
+		chargeEnd = info.charge_end ?? 100;
+	});
+
+	async function setBrightness(percent: number) {
+		brightness = percent;
+		await invoke("set_brightness", { percent });
+	}
+
+	async function setChargeThreshold(which: "start" | "end", percent: number) {
+		if (which === "start") chargeStart = percent;
+		else chargeEnd = percent;
+		await invoke("set_charge_threshold", { which, percent });
+	}
+</script>
+
+<ViewScaffold title="Power">
+	{#if info}
+		<Group title="Battery">
+			{#each info.battery as [label, value] (label)}
+				<InfoRow {label} {value} />
+			{/each}
+			<InfoRow label="Power source" value={info.power_source} />
+		</Group>
+
+		<Group title="Brightness">
+			{#if info.brightness_pct !== null}
+				<Row label="Screen brightness">
+					<input type="range" min="1" max="100" bind:value={brightness} onchange={() => setBrightness(brightness)} />
+					<span class="pct">{brightness}%</span>
+				</Row>
+			{:else}
+				<Hint text="No controllable backlight found." />
+			{/if}
+		</Group>
+
+		{#if info.charge_start !== null && info.charge_end !== null}
+			<Group
+				title="Charge limits"
+				hint="Some laptops let you cap charging below 100% to slow battery wear on a machine that's mostly plugged in."
+			>
+				<Row label="Start charging below (%)">
+					<input type="number" min="0" max="100" bind:value={chargeStart} onchange={() => setChargeThreshold("start", chargeStart)} />
+				</Row>
+				<Row label="Stop charging at (%)">
+					<input type="number" min="1" max="100" bind:value={chargeEnd} onchange={() => setChargeThreshold("end", chargeEnd)} />
+				</Row>
+			</Group>
+		{/if}
+
+		<Group
+			title="TLP"
+			hint="TLP automatically applies a power-saving profile on battery and a performance profile on AC — there's no manual switch by design."
+		>
+			<InfoRow label="Current profile" value={info.tlp_profile ?? "unknown"} />
+		</Group>
+	{/if}
+</ViewScaffold>
+
+<style>
+	input[type="range"] {
+		width: 180px;
+	}
+
+	input[type="number"] {
+		width: 8ch;
+		background-color: var(--bg);
+		color: var(--on-surface);
+		border: 1px solid transparent;
+		border-radius: var(--radius-secondary, 6px);
+		padding: var(--space-xs, 4px) var(--space-sm, 8px);
+	}
+
+	.pct {
+		margin-left: var(--space-sm, 8px);
+		font-size: var(--font-size-secondary, 12px);
+		opacity: 0.7;
+	}
+</style>