Add database schema, encryption utilities, and local database service

- Implement `schema.ts` for SQLite schema creation, indexing, and sync metadata initialization.
- Develop `encryption.ts` with AES-256-GCM encryption utilities for securing database data.
- Add `database.service.ts` to manage CRUD operations with encryption support, user-specific databases, and schema initialization.
- Integrate book, chapter, and character operations with encrypted content handling and sync preparation.

electron/database/mappers/user.mapper.ts

@@ -0,0 +1,153 @@
+/**
+ * TypeScript interfaces (copied from lib/models for type safety)
+ */
+
+export interface Subscription {
+    subType: string;
+    subTier: number;
+    status: boolean;
+}
+
+export interface UserProps {
+    id: string;
+    name: string;
+    lastName: string;
+    username: string;
+    authorName?: string;
+    email?: string;
+    accountVerified: boolean;
+    termsAccepted: boolean;
+    aiUsage: number;
+    apiKeys: {
+        gemini: boolean;
+        openai: boolean;
+        anthropic: boolean;
+    };
+    books?: any[];
+    guideTour?: { [key: string]: boolean }[];
+    subscription?: Subscription[];
+    writingLang: number;
+    writingLevel: number;
+    ritePoints: number;
+    creditsBalance: number;
+    groupId: number;
+}
+
+/**
+ * Database row types (snake_case from SQLite)
+ */
+export interface DBUser {
+    user_id: string;
+    first_name: string;
+    last_name: string;
+    username: string;
+    email: string;
+    origin_email: string;
+    origin_username: string;
+    author_name?: string;
+    origin_author_name?: string;
+    plateform: string;
+    social_id?: string;
+    user_group: number;
+    password?: string;
+    term_accepted: number;
+    verify_code?: string;
+    reg_date: number;
+    account_verified: number;
+    user_meta: string; // JSON containing apiKeys, guideTour, writingLang, writingLevel, aiUsage
+    erite_points: number;
+    stripe_customer_id?: string;
+    credits_balance: number;
+    synced?: number;
+}
+
+interface UserMeta {
+    apiKeys?: {
+        gemini: boolean;
+        openai: boolean;
+        anthropic: boolean;
+    };
+    guideTour?: { [key: string]: boolean }[];
+    subscription?: Subscription[];
+    writingLang?: number;
+    writingLevel?: number;
+    aiUsage?: number;
+}
+
+/**
+ * MAPPERS: DB → TypeScript Interfaces
+ */
+
+export function dbToUser(dbUser: DBUser): UserProps {
+    let meta: UserMeta = {};
+    try {
+        meta = JSON.parse(dbUser.user_meta || '{}');
+    } catch (error) {
+        console.error('Failed to parse user_meta:', error);
+    }
+
+    return {
+        id: dbUser.user_id,
+        name: dbUser.first_name,
+        lastName: dbUser.last_name,
+        username: dbUser.username,
+        authorName: dbUser.author_name,
+        email: dbUser.email,
+        accountVerified: dbUser.account_verified === 1,
+        termsAccepted: dbUser.term_accepted === 1,
+        aiUsage: meta.aiUsage || 0,
+        apiKeys: meta.apiKeys || {
+            gemini: false,
+            openai: false,
+            anthropic: false
+        },
+        books: [], // Populated separately
+        guideTour: meta.guideTour || [],
+        subscription: meta.subscription || [],
+        writingLang: meta.writingLang || 1,
+        writingLevel: meta.writingLevel || 1,
+        ritePoints: dbUser.erite_points,
+        creditsBalance: dbUser.credits_balance,
+        groupId: dbUser.user_group
+    };
+}
+
+/**
+ * MAPPERS: TypeScript Interfaces → DB
+ */
+
+export function userToDb(user: UserProps, synced: number = 0): DBUser {
+    const meta: UserMeta = {
+        apiKeys: user.apiKeys,
+        guideTour: user.guideTour,
+        subscription: user.subscription,
+        writingLang: user.writingLang,
+        writingLevel: user.writingLevel,
+        aiUsage: user.aiUsage
+    };
+
+    return {
+        user_id: user.id,
+        first_name: user.name,
+        last_name: user.lastName,
+        username: user.username,
+        email: user.email || '',
+        origin_email: user.email || '',
+        origin_username: user.username,
+        author_name: user.authorName,
+        origin_author_name: user.authorName,
+        plateform: 'electron',
+        social_id: undefined,
+        user_group: user.groupId,
+        password: undefined,
+        term_accepted: user.termsAccepted ? 1 : 0,
+        verify_code: undefined,
+        reg_date: Date.now(),
+        account_verified: user.accountVerified ? 1 : 0,
+        user_meta: JSON.stringify(meta),
+        erite_points: user.ritePoints,
+        stripe_customer_id: undefined,
+        credits_balance: user.creditsBalance,
+        synced
+    };
+}