Improve the reliability of the task management system by fixing errors

Update database schema to allow nullable fields for invoice reference and amount, adjust React components for safe access to optional data, and remove obsolete client-side debugging scripts.

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/mpVybiP

sql/fix_references.sql

@@ -7,8 +7,8 @@ INSERT INTO suppliers (name, contact) VALUES
 ON CONFLICT DO NOTHING;
 
 -- 2. Créer des données de test minimales pour groups  
-INSERT INTO groups (name, description) VALUES 
-('Magasin Test', 'Magasin de test pour avoirs')
+INSERT INTO groups (name, color) VALUES 
+('Magasin Test', '#1976D2')
 ON CONFLICT DO NOTHING;
 
 -- 3. Vérifier/créer un utilisateur admin