styling(core): add star background

src/app/core/components/background/background.html

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+<canvas #canvas></canvas>

src/app/core/components/background/background.scss

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+canvas {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    z-index: -1;
+}

src/app/core/components/background/background.ts

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+import { Component, ElementRef, HostListener, ViewChild } from '@angular/core';
+
+@Component({
+  selector: 'app-background',
+  imports: [],
+  templateUrl: './background.html',
+  styleUrl: './background.scss'
+})
+export class Background {
+
+  @ViewChild('canvas', { static: true }) canvasRef!: ElementRef<HTMLCanvasElement>;
+
+  // Config
+  private numStars = 150;
+  private minBlink = 0.2;
+  private maxBlink = 1;
+  private blinkSpeed = 0.002;    // Stern blinkt langsamer oder schneller
+  private maxSpeed = 0.1;        // Sternbewegungsgeschwindigkeit
+  private parallaxFactor = 0.5; // Scroll-Parallax-Faktor
+
+  // Feature toggles
+  private enableBlink = true;
+  private enableMovement = true;
+
+  private ctx!: CanvasRenderingContext2D;
+  private stars: Star[] = [];
+  private width = window.innerWidth;
+  private height = window.innerHeight;
+  private animationId!: number;
+  private scrollY = window.scrollY;
+
+  ngOnInit() {
+    const canvas = this.canvasRef.nativeElement;
+    this.ctx = canvas.getContext('2d')!;
+    canvas.width = this.width;
+    canvas.height = this.height;
+
+    for (let i = 0; i < (this.numStars) * (document.body.scrollHeight / this.height); i++) {
+      this.stars.push({
+        x: Math.random() * this.width,
+        y: Math.random() * document.body.scrollHeight,
+        radius: Math.random() * 1.5 + 0.5,
+        alpha: this.minBlink + Math.random() * (this.maxBlink - this.minBlink),
+        alphaChange: (Math.random() * this.blinkSpeed) + 0.0005,
+        vx: (Math.random() - 0.5) * this.maxSpeed,
+        vy: (Math.random() - 0.5) * this.maxSpeed
+      });
+    }
+
+    this.animate();
+  }
+
+  @HostListener('window:resize')
+  onResize() {
+    this.width = window.innerWidth;
+    this.height = window.innerHeight;
+    const canvas = this.canvasRef.nativeElement;
+    canvas.width = this.width;
+    canvas.height = this.height;
+  }
+
+  @HostListener('window:scroll')
+  onScroll() {
+    this.scrollY = window.scrollY;
+  }
+
+  private animate() {
+    const ctx = this.ctx;
+    ctx.clearRect(0, 0, this.width, this.height);
+
+    for (let star of this.stars) {
+      // Blinken
+      if (this.enableBlink) {
+        star.alpha += star.alphaChange;
+        if (star.alpha > this.maxBlink || star.alpha < this.minBlink) star.alphaChange *= -1;
+      }
+
+      // Bewegung
+      if (this.enableMovement) {
+        star.x += star.vx;
+        star.y += star.vy;
+      }
+
+      // Stern zeichnen mit Scroll-Parallax
+      ctx.beginPath();
+      ctx.arc(star.x, star.y - this.scrollY * this.parallaxFactor, star.radius, 0, Math.PI * 2);
+      ctx.fillStyle = `rgba(255, 215, 0, ${star.alpha})`; // gold
+      ctx.fill();
+    }
+
+    this.animationId = requestAnimationFrame(() => this.animate());
+  }
+
+  ngOnDestroy() {
+    cancelAnimationFrame(this.animationId);
+  }
+  
+}
+
+interface Star {
+  x: number;
+  y: number;
+  radius: number;
+  alpha: number;
+  alphaChange: number;
+  vx: number;
+  vy: number;
+}