Remove Story model handling verbal styles and linguistic properties

- Delete `Story` model implementation including `getVerbesStyle` method and related properties.
- Cleanup unused interfaces and redundant logic from the codebase.

electron/database/keyManager.ts

@@ -0,0 +1,48 @@
+import Store from 'electron-store';
+
+/**
+ * Key Manager - Manages user encryption keys stored in electron-store
+ */
+
+const store = new Store({
+    encryptionKey: 'eritors-scribe-secure-key'
+});
+
+/**
+ * Get user encryption key from secure store
+ * @param userId - User ID
+ * @returns User's encryption key or null if not found
+ */
+export function getUserEncryptionKey(userId: string): string {
+    const key: string | undefined = store.get(`encryptionKey-${userId}`) as string | undefined;
+    if (key === undefined) {
+        throw new Error(`Unknown encryptionKey`);
+    }
+    return key;
+}
+
+/**
+ * Set user encryption key in secure store
+ * @param userId - User ID
+ * @param encryptionKey - Encryption key to store
+ */
+export function setUserEncryptionKey(userId: string, encryptionKey: string): void {
+    store.set(`encryptionKey-${userId}`, encryptionKey);
+}
+
+/**
+ * Check if user has an encryption key
+ * @param userId - User ID
+ * @returns True if key exists
+ */
+export function hasUserEncryptionKey(userId: string): boolean {
+    return store.has(`encryptionKey-${userId}`);
+}
+
+/**
+ * Delete user encryption key
+ * @param userId - User ID
+ */
+export function deleteUserEncryptionKey(userId: string): void {
+    store.delete(`encryptionKey-${userId}`);
+}