feat(layout): add ParticlesBackground component and conditional rendering based on browser environment

- Introduced the `ParticlesBackground` component to enhance the visual experience in the layout.
- Updated the header rendering logic to conditionally display based on the browser environment, ensuring compatibility with server-side rendering.

src/lib/components/effects/ParticlesBackground.svelte

@@ -0,0 +1,176 @@
+<script lang="ts">
+	import { onMount, onDestroy } from 'svelte';
+	import { browser } from '$app/environment';
+
+	/** Number of particles (tuned for desktop background) */
+	const PARTICLE_COUNT = 80;
+	/** Max distance to draw a line between two particles */
+	const LINE_DISTANCE = 120;
+	/** Particle base speed */
+	const SPEED = 0.2;
+	/** Mouse influence: radius and repulsion strength */
+	const MOUSE_RADIUS = 200;
+	const MOUSE_STRENGTH = 0.08;
+
+	interface Particle {
+		x: number;
+		y: number;
+		vx: number;
+		vy: number;
+		radius: number;
+	}
+
+	let canvasEl: HTMLCanvasElement | null = $state(null);
+	let ctx: CanvasRenderingContext2D | null = null;
+	let particles: Particle[] = [];
+	let animationId = 0;
+	let isDesktop = $state(false);
+	/** Mouse position in viewport coords (updated on mousemove, read in draw) */
+	let mouseX = 0;
+	let mouseY = 0;
+	let mouseActive = false;
+
+	function initParticles(width: number, height: number): void {
+		particles = Array.from({ length: PARTICLE_COUNT }, () => ({
+			x: Math.random() * width,
+			y: Math.random() * height,
+			vx: (Math.random() - 0.5) * SPEED,
+			vy: (Math.random() - 0.5) * SPEED,
+			radius: Math.random() * 1.2 + 0.6
+		}));
+	}
+
+	function draw(): void {
+		if (!ctx || !canvasEl) return;
+		const cssW = canvasEl.offsetWidth;
+		const cssH = canvasEl.offsetHeight;
+		const isDark = document.documentElement.classList.contains('dark');
+
+		ctx.clearRect(0, 0, cssW, cssH);
+
+		// Particle color: subtle, theme-aware
+		const dotColor = isDark ? 'rgba(148, 163, 184, 0.35)' : 'rgba(100, 116, 139, 0.28)';
+		const lineColor = isDark ? 'rgba(148, 163, 184, 0.12)' : 'rgba(100, 116, 139, 0.1)';
+
+		// Update and draw particles (coordinates in CSS pixels; ctx is scaled by dpr in resize)
+		for (let i = 0; i < particles.length; i++) {
+			const p = particles[i];
+			// Gentle repulsion from mouse
+			if (mouseActive) {
+				const dx = p.x - mouseX;
+				const dy = p.y - mouseY;
+				const dist = Math.hypot(dx, dy);
+				if (dist > 0 && dist < MOUSE_RADIUS) {
+					const falloff = 1 - dist / MOUSE_RADIUS;
+					const force = (MOUSE_STRENGTH * falloff) / dist;
+					p.vx += dx * force;
+					p.vy += dy * force;
+				}
+			}
+			p.x += p.vx;
+			p.y += p.vy;
+			if (p.x < 0 || p.x > cssW) p.vx *= -1;
+			if (p.y < 0 || p.y > cssH) p.vy *= -1;
+			p.x = Math.max(0, Math.min(cssW, p.x));
+			p.y = Math.max(0, Math.min(cssH, p.y));
+
+			ctx.beginPath();
+			ctx.arc(p.x, p.y, p.radius, 0, Math.PI * 2);
+			ctx.fillStyle = dotColor;
+			ctx.fill();
+		}
+
+		// Draw lines between nearby particles
+		ctx.strokeStyle = lineColor;
+		ctx.lineWidth = 0.8;
+		for (let i = 0; i < particles.length; i++) {
+			for (let j = i + 1; j < particles.length; j++) {
+				const dx = particles[i].x - particles[j].x;
+				const dy = particles[i].y - particles[j].y;
+				const dist = Math.hypot(dx, dy);
+				if (dist < LINE_DISTANCE) {
+					const alpha = 1 - dist / LINE_DISTANCE;
+					ctx.globalAlpha = alpha;
+					ctx.beginPath();
+					ctx.moveTo(particles[i].x, particles[i].y);
+					ctx.lineTo(particles[j].x, particles[j].y);
+					ctx.stroke();
+					ctx.globalAlpha = 1;
+				}
+			}
+		}
+	}
+
+	function tick(): void {
+		draw();
+		animationId = requestAnimationFrame(tick);
+	}
+
+	function resize(): void {
+		if (!canvasEl || !browser) return;
+		const dpr = Math.min(2, window.devicePixelRatio || 1);
+		const w = canvasEl.offsetWidth;
+		const h = canvasEl.offsetHeight;
+		canvasEl.width = w * dpr;
+		canvasEl.height = h * dpr;
+		const ctx2 = canvasEl.getContext('2d');
+		if (ctx2) {
+			ctx2.scale(dpr, dpr);
+			ctx = ctx2;
+		}
+		initParticles(w, h);
+	}
+
+	function onMouseMove(e: MouseEvent): void {
+		mouseX = e.clientX;
+		mouseY = e.clientY;
+		// Only react when cursor is inside viewport (document mouseleave doesn't fire when leaving window)
+		mouseActive =
+			e.clientX >= 0 &&
+			e.clientY >= 0 &&
+			e.clientX <= (browser ? window.innerWidth : 0) &&
+			e.clientY <= (browser ? window.innerHeight : 0);
+	}
+
+	$effect(() => {
+		if (!browser || !isDesktop || !canvasEl) return;
+		resize();
+		ctx = canvasEl.getContext('2d');
+		if (ctx) tick();
+		window.addEventListener('resize', resize);
+		document.addEventListener('mousemove', onMouseMove);
+		return () => {
+			cancelAnimationFrame(animationId);
+			window.removeEventListener('resize', resize);
+			document.removeEventListener('mousemove', onMouseMove);
+		};
+	});
+
+	onMount(() => {
+		if (!browser) return;
+		const mq = window.matchMedia('(min-width: 1024px)');
+		isDesktop = mq.matches;
+		const handler = (e: MediaQueryListEvent) => {
+			isDesktop = e.matches;
+		};
+		mq.addEventListener('change', handler);
+		return () => mq.removeEventListener('change', handler);
+	});
+
+	onDestroy(() => {
+		cancelAnimationFrame(animationId);
+	});
+</script>
+
+{#if browser && isDesktop}
+	<div
+		class="particles-bg fixed inset-0 pointer-events-none z-0 overflow-hidden"
+		aria-hidden="true"
+	>
+		<canvas
+			bind:this={canvasEl}
+			class="absolute inset-0 w-full h-full"
+			style="width: 100%; height: 100%;"
+		></canvas>
+	</div>
+{/if}

src/routes/+layout.svelte

@@ -2,6 +2,7 @@
 	import { onMount } from 'svelte';
 	import { goto } from '$app/navigation';
 	import { page } from '$app/stores';
+	import { browser } from '$app/environment';
 	import { Toaster } from 'svelte-sonner';
 	import './app.css';
 	import favicon from '$lib/assets/favicon.svg';
@@ -11,6 +12,7 @@
 	import { Switch } from '$lib/components/ui/switch/index.js';
 	import LogOutIcon from '@lucide/svelte/icons/log-out';
 	import MoonIcon from '@lucide/svelte/icons/moon';
+	import ParticlesBackground from '$lib/components/effects/ParticlesBackground.svelte';
 
 	let { data, children } = $props();
 	let cleanupRealtime: (() => void) | undefined;
@@ -78,8 +80,13 @@
 	}}
 />
 
-{#if showHeader}
+{#if browser && showHeader}
-	<header class="border-border flex h-14 shrink-0 items-center justify-end gap-2 border-b px-4 md:px-6">
+	<ParticlesBackground />
+{/if}
+
+<div class="relative z-[1] flex min-h-screen flex-col">
+	{#if showHeader}
+		<header class="border-border flex h-14 shrink-0 items-center justify-end gap-2 border-b px-4 md:px-6">
 		<DropdownMenu.Root>
 			<DropdownMenu.Trigger
 				class="rounded-full outline-none focus-visible:ring-2 focus-visible:ring-ring"
@@ -121,6 +128,7 @@
 			</DropdownMenu.Content>
 		</DropdownMenu.Root>
 	</header>
-{/if}
+	{/if}
 
-{@render children()}
+	{@render children()}
+</div>