feat(01-05): forest screen with level map and complete app flow

- Add forest overview screen with 6-level map showing locked/current/completed states
- Create src/forest/scene.ts with getLevelStatus, renderLevelMap, initForestScreen
- Wire complete flow: welcome -> forest -> lesson -> forest with progress updates
- Add forest CSS with level card styles and continue button

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/styles/main.css

@@ -162,6 +162,103 @@ h3 {
 	cursor: not-allowed;
 }
 
+/* Forest screen */
+.forest {
+	display: flex;
+	flex-direction: column;
+	align-items: center;
+	padding: 2rem;
+	min-height: 100vh;
+	background: var(--bg-forest);
+}
+
+.forest__title {
+	font-family: "Quicksand", sans-serif;
+	font-size: 2rem;
+	color: var(--text-dark);
+	margin-bottom: 1.5rem;
+}
+
+.forest__level-map {
+	display: grid;
+	grid-template-columns: repeat(3, 1fr);
+	gap: 1rem;
+	max-width: 500px;
+	width: 100%;
+	margin-bottom: 2rem;
+}
+
+.level-card {
+	display: flex;
+	flex-direction: column;
+	align-items: center;
+	gap: 0.3rem;
+	padding: 1rem;
+	border-radius: 12px;
+	border: 2px solid transparent;
+	font-family: "Nunito", sans-serif;
+	cursor: pointer;
+	transition:
+		transform 0.2s ease,
+		border-color 0.2s ease;
+	background: white;
+}
+
+.level-card:hover:not(:disabled) {
+	transform: scale(1.05);
+}
+
+.level-card--current {
+	border-color: var(--accent-gold);
+	background: #fff8e0;
+	box-shadow: 0 2px 8px rgba(232, 184, 75, 0.3);
+}
+
+.level-card--completed {
+	border-color: var(--accent-green);
+	background: #e8f5e4;
+}
+
+.level-card--locked {
+	opacity: 0.5;
+	cursor: not-allowed;
+	background: #f0f0f0;
+}
+
+.level-card__number {
+	font-weight: 700;
+	font-size: 0.9rem;
+	color: var(--text-dark);
+}
+
+.level-card__keys {
+	font-family: "Quicksand", sans-serif;
+	font-weight: 600;
+	font-size: 1.1rem;
+	color: var(--accent-purple);
+}
+
+.level-card__status {
+	font-size: 1.2rem;
+}
+
+.forest__continue-btn {
+	padding: 1rem 3rem;
+	border-radius: 12px;
+	background: var(--accent-green);
+	color: white;
+	border: none;
+	font-family: "Quicksand", sans-serif;
+	font-weight: 700;
+	font-size: 1.3rem;
+	cursor: pointer;
+	transition: transform 0.2s ease;
+}
+
+.forest__continue-btn:hover {
+	transform: scale(1.05);
+}
+
 /* Lesson screen */
 .lesson {
 	display: flex;