feat: add welcome lesson, DVD bounce animation, mobile layout reorder

- Add Welcome module with intro lessons (EN/DE)
- Success message now bounces like DVD screensaver (10s duration)
- Mobile: nav bar at top, preview before editor
- Logo: CODE with purple background pill

src/main.css

@@ -589,27 +589,42 @@ code, kbd {
 .preview-wrapper.matched::after {
 	content: "CRISPY! ٩(◕‿◕)۶";
 	position: absolute;
-	top: 50%;
-	left: 50%;
-	transform: translate(-50%, -50%);
 	background: var(--success-color);
 	color: white;
 	padding: var(--spacing-sm) var(--spacing-lg);
 	border-radius: var(--border-radius-lg);
 	font-weight: bold;
 	font-size: 1.1rem;
-	animation: pop-in 0.4s ease-out;
+	animation: dvd-bounce 8s ease-in-out infinite;
 	z-index: 10;
+	white-space: nowrap;
 }
 
-@keyframes pop-in {
+@keyframes dvd-bounce {
 	0% {
-		transform: translate(-50%, -50%) scale(0.8);
-		opacity: 0;
+		top: 10%;
+		left: 10%;
+		transform: scale(1);
+	}
+	25% {
+		top: 70%;
+		left: 80%;
+		transform: scale(1.1);
+	}
+	50% {
+		top: 20%;
+		left: 70%;
+		transform: scale(0.95);
+	}
+	75% {
+		top: 60%;
+		left: 15%;
+		transform: scale(1.05);
 	}
 	100% {
-		transform: translate(-50%, -50%) scale(1);
-		opacity: 1;
+		top: 10%;
+		left: 10%;
+		transform: scale(1);
 	}
 }
 
@@ -1111,40 +1126,41 @@ input:checked + .toggle-slider::before {
 		width: 100%;
 		flex-shrink: 0;
 		border-right: none;
+		display: contents;
 	}
 
-	.left-panel {
-		min-height: 80vh;
-		border-bottom: 1px solid var(--border-color);
-	}
-
-	.right-panel {
-		min-height: 50vh;
+	/* Mobile order: nav -> instructions -> preview -> editor */
+	.game-controls {
+		order: 1;
+		padding: var(--spacing-sm);
 	}
 
 	.instructions {
+		order: 2;
 		max-height: none;
 		overflow-y: visible;
 	}
 
+	.preview-section {
+		order: 3;
+	}
+
 	.editor-section {
+		order: 4;
 		flex: 1;
 		min-height: 50vh;
 	}
 
+	.preview-wrapper {
+		margin: var(--spacing-sm);
+		min-height: 40vh;
+	}
+
 	.editor-content {
 		flex: 1;
 		min-height: 45vh;
 	}
 
-	.preview-wrapper {
-		margin: var(--spacing-sm);
-	}
-
-	.game-controls {
-		padding: var(--spacing-sm);
-	}
-
 	.module-pill {
 		flex: 1;
 		margin: 0 var(--spacing-sm);