fix(backup): resolve real admin user ID instead of hardcoded 'system' for automatic backups

Fixes FK violation: database_backups.created_by -> users.id
The 'system' user does not exist in the users table, causing
INSERT failures every hour for scheduled backups.

server/backupService.ts

@@ -5,7 +5,7 @@ import path from 'path';
 import { nanoid } from 'nanoid';
 import { eq, desc } from "drizzle-orm";
 import { db } from "./db";
-import { databaseBackups, utilities } from "@shared/schema";
+import { databaseBackups, utilities, users } from "@shared/schema";
 import type { DatabaseBackup, InsertDatabaseBackup } from "@shared/schema";
 
 const execAsync = promisify(exec);
@@ -70,6 +70,31 @@ export class BackupService {
     };
   }
 
+  /**
+   * Resolve a valid user ID for system-initiated backups.
+   * Returns the first admin user ID, or the first user if no admin exists.
+   * This avoids FK violations on database_backups.created_by -> users.id.
+   */
+  private async resolveSystemUserId(): Promise<string | null> {
+    try {
+      // Try to find an admin user first
+      const [adminUser] = await db.select({ id: users.id })
+        .from(users)
+        .where(eq(users.role, 'admin'))
+        .limit(1);
+      if (adminUser) return adminUser.id;
+
+      // Fallback: any existing user
+      const [anyUser] = await db.select({ id: users.id })
+        .from(users)
+        .limit(1);
+      return anyUser?.id ?? null;
+    } catch (error) {
+      console.error('❌ Failed to resolve system user ID for backup:', error);
+      return null;
+    }
+  }
+
   async createBackup(type: 'manual' | 'automatic' = 'manual', createdBy: string = 'system'): Promise<DatabaseBackup> {
     try {
       const id = nanoid();
@@ -240,10 +265,20 @@ export class BackupService {
       const lastBackup = existingBackupToday[0];
       const lastBackupDate = lastBackup ? lastBackup.createdAt.toISOString().split('T')[0] : null;
 
-      // Si aucune sauvegarde automatique aujourd'hui, en créer une
+      // Only perform backup if no automatic backup exists for today
       if (lastBackupDate !== today) {
+        // Resolve a real user ID if called with default 'system'
+        let resolvedUserId = userId;
+        if (userId === 'system') {
+          const systemId = await this.resolveSystemUserId();
+          if (!systemId) {
+            console.warn('⚠️ No user found in database — skipping daily backup');
+            return { backupPerformed: false, message: 'Aucun utilisateur trouvé pour la sauvegarde' };
+          }
+          resolvedUserId = systemId;
+        }
         console.log('🔄 Première connexion du jour - Création de la sauvegarde automatique...');
-        await this.createBackup('automatic', userId);
+        await this.createBackup('automatic', resolvedUserId);
         console.log('✅ Sauvegarde quotidienne effectuée avec succès');
         return {
           backupPerformed: true,
@@ -298,8 +333,14 @@ export class BackupService {
 
           // Only proceed if no automatic backup exists for today
           if (lastBackupDate !== today) {
+            // Resolve a real user ID to satisfy FK constraint
+            const systemUserId = await this.resolveSystemUserId();
+            if (!systemUserId) {
+              console.warn('⚠️ No user found in database — skipping automatic backup');
+              return;
+            }
             console.log('🔄 Starting automatic backup...');
-            await this.createBackup('automatic', 'system');
+            await this.createBackup('automatic', systemUserId);
             this.lastAutomaticBackupDate = today;
             console.log('✅ Automatic backup completed');
           }