feat(03-02): lesson screen 3-phase state machine with review and repetition

- Discover phase: companion introduces new key, key pulses, child presses once
- Practice phase: existing letter exercise with cumulative stats
- Words phase: word display with active letter highlighting
- Review mode skips discover, mixes letters/words from recent levels
- Encouragement messages for repetition protection
- Phase indicator UI (Entdecken / Ueben / Woerter)
- CSS for word display, phase indicator, discover pulse animation

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

src/styles/main.css

@@ -685,3 +685,54 @@ h3 {
 	transform: scale(0.9) !important;
 	animation: none;
 }
+
+/* Lesson phase indicator */
+.lesson__phase-indicator {
+	text-align: center;
+	font-family: var(--font-heading);
+	font-size: 1rem;
+	color: var(--text-warm);
+	margin-bottom: 0.5rem;
+	opacity: 0.7;
+}
+
+/* Word display for Woerter phase */
+.word-display {
+	display: flex;
+	justify-content: center;
+	gap: 0.25rem;
+	font-family: var(--font-heading);
+	font-size: 2.5rem;
+	margin: 2rem 0;
+}
+
+.word-display__letter {
+	color: var(--text-light);
+	transition: color 0.3s;
+}
+
+.word-display__letter--active {
+	color: var(--accent-gold);
+	font-weight: 700;
+}
+
+.word-display__letter--done {
+	color: var(--accent-green);
+}
+
+/* Discover phase key pulse */
+.keyboard__key--discover-pulse {
+	animation: discover-pulse 1.5s ease-in-out infinite;
+}
+
+@keyframes discover-pulse {
+	0%,
+	100% {
+		transform: scale(1);
+		box-shadow: 0 0 0 0 var(--accent-gold);
+	}
+	50% {
+		transform: scale(1.1);
+		box-shadow: 0 0 12px 4px var(--accent-gold);
+	}
+}