feat(02-03): add IndexedDB accessor methods for companionAssets, styleReference, forestElements

- saveCompanionAssets/getCompanionAssets keyed by characterType
- saveStyleReference/getStyleReference singleton pattern (id: 1)
- saveForestElement (auto-increment add) / getForestElements (getAll)
- Extended type imports for CompanionAssets, CompanionType, ForestElement, StyleReference

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

src/storage/db.ts

@@ -1,4 +1,11 @@
-import type { Progress, Settings } from "../types";
+import type {
+	CompanionAssets,
+	CompanionType,
+	ForestElement,
+	Progress,
+	Settings,
+	StyleReference,
+} from "../types";
 
 const DB_NAME = "zauberwald";
 const DB_VERSION = 1;
@@ -68,3 +75,63 @@ export function saveSettings(db: IDBDatabase, settings: Settings): Promise<void>
 		request.onerror = () => reject(request.error);
 	});
 }
+
+export function saveCompanionAssets(db: IDBDatabase, assets: CompanionAssets): Promise<void> {
+	return new Promise((resolve, reject) => {
+		const tx = db.transaction("companionAssets", "readwrite");
+		const store = tx.objectStore("companionAssets");
+		const request = store.put(assets);
+		request.onsuccess = () => resolve();
+		request.onerror = () => reject(request.error);
+	});
+}
+
+export function getCompanionAssets(db: IDBDatabase, characterType: CompanionType): Promise<CompanionAssets | null> {
+	return new Promise((resolve, reject) => {
+		const tx = db.transaction("companionAssets", "readonly");
+		const store = tx.objectStore("companionAssets");
+		const request = store.get(characterType);
+		request.onsuccess = () => resolve((request.result as CompanionAssets) ?? null);
+		request.onerror = () => reject(request.error);
+	});
+}
+
+export function saveStyleReference(db: IDBDatabase, ref: StyleReference): Promise<void> {
+	return new Promise((resolve, reject) => {
+		const tx = db.transaction("styleReference", "readwrite");
+		const store = tx.objectStore("styleReference");
+		const request = store.put(ref);
+		request.onsuccess = () => resolve();
+		request.onerror = () => reject(request.error);
+	});
+}
+
+export function getStyleReference(db: IDBDatabase): Promise<StyleReference | null> {
+	return new Promise((resolve, reject) => {
+		const tx = db.transaction("styleReference", "readonly");
+		const store = tx.objectStore("styleReference");
+		const request = store.get(1);
+		request.onsuccess = () => resolve((request.result as StyleReference) ?? null);
+		request.onerror = () => reject(request.error);
+	});
+}
+
+export function saveForestElement(db: IDBDatabase, element: ForestElement): Promise<number> {
+	return new Promise((resolve, reject) => {
+		const tx = db.transaction("forestElements", "readwrite");
+		const store = tx.objectStore("forestElements");
+		const request = store.add(element);
+		request.onsuccess = () => resolve(request.result as number);
+		request.onerror = () => reject(request.error);
+	});
+}
+
+export function getForestElements(db: IDBDatabase): Promise<ForestElement[]> {
+	return new Promise((resolve, reject) => {
+		const tx = db.transaction("forestElements", "readonly");
+		const store = tx.objectStore("forestElements");
+		const request = store.getAll();
+		request.onsuccess = () => resolve((request.result as ForestElement[]) ?? []);
+		request.onerror = () => reject(request.error);
+	});
+}