feat(accounts): add account settings service

- Add AccountsSettingsService for managing account-related settings
- Update validators, create and edit services to use settings
- Add constants for account configuration
- Update frontend utils and translations

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/server/src/modules/Accounts/AccountsSettings.service.ts

@@ -0,0 +1,33 @@
+import { Inject, Injectable } from '@nestjs/common';
+import { SettingsStore } from '../Settings/SettingsStore';
+import { SETTINGS_PROVIDER } from '../Settings/Settings.types';
+
+export interface IAccountsSettings {
+  accountCodeRequired: boolean;
+  accountCodeUnique: boolean;
+}
+
+@Injectable()
+export class AccountsSettingsService {
+  constructor(
+    @Inject(SETTINGS_PROVIDER)
+    private readonly settingsStore: () => SettingsStore,
+  ) {}
+
+  /**
+   * Retrieves account settings (account code required, account code unique).
+   */
+  public async getAccountsSettings(): Promise<IAccountsSettings> {
+    const settingsStore = await this.settingsStore();
+    return {
+      accountCodeRequired: settingsStore.get(
+        { group: 'accounts', key: 'account_code_required' },
+        false,
+      ),
+      accountCodeUnique: settingsStore.get(
+        { group: 'accounts', key: 'account_code_unique' },
+        true,
+      ),
+    };
+  }
+}