Add comprehensive diagnostic tests for database connectivity and operations

Add SQL script with diagnostic queries to test table existence, manual record insertion, and record deletion, ensuring proper database functionality.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 9fcf4b21-eb0c-4e53-a567-e2ce4a6ad869
Replit-Commit-Checkpoint-Type: full_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/test_server_connection.sql

@@ -0,0 +1,32 @@
+-- 🔍 TEST DE DIAGNOSTIC COMPLET
+-- Vérifiez que tout fonctionne côté base de données
+
+-- 1. La table existe-t-elle vraiment ?
+SELECT COUNT(*) as table_count
+FROM information_schema.tables 
+WHERE table_name = 'avoirs' AND table_schema = 'public';
+
+-- 2. Test d'insertion manuelle pour voir si ça marche
+INSERT INTO avoirs (
+    supplier_id, 
+    group_id, 
+    invoice_reference, 
+    amount, 
+    comment, 
+    commercial_processed, 
+    created_by
+) VALUES (
+    1,  -- Remplacez par un ID supplier existant
+    1,  -- Remplacez par un ID group existant
+    'TEST-MANUEL-' || EXTRACT(EPOCH FROM NOW()),
+    25.99,
+    'Test diagnostic manuel',
+    false,
+    'admin'  -- Remplacez par un user_id existant
+) RETURNING id, created_at;
+
+-- 3. Vérifiez le résultat
+SELECT COUNT(*) as total_avoirs FROM avoirs;
+
+-- 4. Supprimez le test
+DELETE FROM avoirs WHERE comment = 'Test diagnostic manuel';