feat(05-02): fix reward flow and call sites for paginated forest

- Import SLOTS_PER_PAGE in reward.ts; replace hardcoded 12 with it
- Import SLOTS_PER_PAGE and getForestElements in app.ts
- Zurueck zum Wald callback navigates to page containing new element
- currentForestPage updated in progress before initForestScreen

src/app.ts

@@ -3,8 +3,8 @@ import { companions } from "./companion/characters";
 import { getGreeting } from "./companion/companion";
 import { renderInlineMarkdown } from "./utils/markdown";
 import { initRewardScreen, startPreGeneration } from "./forest/reward";
-import { initForestScreen, renderForestScene } from "./forest/scene";
-import { getProgress, openDB, saveProgress } from "./storage/db";
+import { initForestScreen, renderForestScene, SLOTS_PER_PAGE } from "./forest/scene";
+import { getForestElements, getProgress, openDB, saveProgress } from "./storage/db";
 import type { ScreenName } from "./types";
 import { initParentScreen, showParentCodePrompt } from "./ui/parent";
 import { initLessonScreen, initWelcomeScreen } from "./ui/screens";
@@ -119,11 +119,19 @@ async function handleLessonComplete(
 			);
 		},
 		async () => {
-			// "Zurück zum Wald" -- show forest with new element animated
+			// "Zurück zum Wald" -- navigate to page containing the new element
+			const elements = await getForestElements(db);
+			const newPage = Math.max(0, Math.ceil(elements.length / SLOTS_PER_PAGE) - 1);
+
+			// Update progress with new page before initForestScreen reads it
+			const latestProgress = await getProgress(db);
+			if (latestProgress) {
+				latestProgress.currentForestPage = newPage;
+				await saveProgress(db, latestProgress);
+			}
+
 			await initForestScreen(db, startLessonFromForest);
-			const prog = await getProgress(db);
-			const page = prog?.currentForestPage ?? 0;
-			await renderForestScene(db, page, elementId);
+			await renderForestScene(db, newPage, elementId);
 			showScreen("forest");
 		},
 	);

src/forest/reward.ts

@@ -23,6 +23,7 @@ import type { CompanionType, ForestElement } from "../types";
 import { playRewardSound } from "../audio/sounds";
 import { speakText } from "../audio/speech";
 import { renderInlineMarkdown } from "../utils/markdown";
+import { SLOTS_PER_PAGE } from "./scene";
 
 // --- Element types for random selection ---
 
@@ -176,7 +177,7 @@ export async function initRewardScreen(
 
 	// 4. Determine grid position for new element
 	const existing = await getForestElements(db);
-	const slotIndex = existing.length % 12;
+	const slotIndex = existing.length % SLOTS_PER_PAGE;
 	const col = slotIndex % 4;
 	const row = Math.floor(slotIndex / 4);
 	// Add small random offset for natural feel