Add simple diagnostic queries for production database analysis

Adds a SQL script with basic queries to count records in suppliers, groups, and users tables, and retrieve initial entries from each.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 9fcf4b21-eb0c-4e53-a567-e2ce4a6ad869
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/9fcf4b21-eb0c-4e53-a567-e2ce4a6ad869/2Jd7tYp

sql/diagnostic_simple_production.sql

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+-- 🔍 DIAGNOSTIC SIMPLE - Une requête à la fois
+-- Copiez chaque ligne et exécutez séparément
+
+-- 1. Combien d'enregistrements dans chaque table ?
+SELECT COUNT(*) FROM suppliers;
+
+-- 2. 
+SELECT COUNT(*) FROM groups;  
+
+-- 3.
+SELECT COUNT(*) FROM users;
+
+-- 4. Si suppliers > 0, affichez les premiers
+SELECT id, name FROM suppliers LIMIT 3;
+
+-- 5. Si groups > 0, affichez les premiers  
+SELECT id, name FROM groups LIMIT 3;
+
+-- 6. Si users > 0, affichez les premiers
+SELECT id, username FROM users LIMIT 3;