refactor: implement database service with strategy pattern

- Add DatabaseService with MockDatabaseStrategy and ProductionDatabaseStrategy
- Use strategy pattern to switch between test and production database implementations
- Improve type safety and testability of database operations
- Update database seeder to use new database service architecture

This is the foundation for modernizing the database layer.

services/database.seeder.ts

@@ -1,4 +1,4 @@
-import { dbService } from './couchdb.factory';
+import { databaseService } from './database';
 import { AccountStatus } from './auth/auth.constants';
 import { UserRole } from '../types';
 
@@ -15,7 +15,7 @@ export class DatabaseSeeder {
 
     try {
       // Check if admin already exists
-      const existingAdmin = await dbService.findUserByEmail(adminEmail);
+      const existingAdmin = await databaseService.findUserByEmail(adminEmail);
 
       if (existingAdmin) {
         console.warn('✅ Default admin user already exists');
@@ -33,7 +33,7 @@ export class DatabaseSeeder {
             status: AccountStatus.ACTIVE,
             emailVerified: true,
           };
-          await dbService.updateUser(updatedAdmin);
+          await databaseService.updateUser(updatedAdmin);
           console.warn('✅ Admin user updated successfully');
           console.warn('👤 Updated admin:', updatedAdmin);
         }
@@ -42,7 +42,7 @@ export class DatabaseSeeder {
 
       console.warn('🚀 Creating new admin user...');
       // Create default admin user
-      const adminUser = await dbService.createUserWithPassword(
+      const adminUser = await databaseService.createUserWithPassword(
         adminEmail,
         adminPassword,
         'admin'
@@ -60,7 +60,7 @@ export class DatabaseSeeder {
         lastLoginAt: new Date(),
       };
 
-      await dbService.updateUser(updatedAdmin);
+      await databaseService.updateUser(updatedAdmin);
 
       console.warn('✅ Admin user created successfully');
       console.warn('👤 Final admin user:', updatedAdmin);