feat: Système notifications complet

feat: Notifications complètes - rappels examens + détection nouveautés

feat: Notifications push Firebase Cloud Messaging (FCM)

feat: API notifications rappel 1h pour examens/évaluations

feat: API notifications rappel 1h avant deadline

fix: Correction signatures fonctions notifications (remove current_user param)

docs: Ajout endpoints notifications dans documentation API

feat: Ajout routes notifications pour création projet/groupe

Add projects management: create projects, list projects, mark complete, and link groups to projects

Add endpoint to list student's groups

Fix: create_groups parameter and equitable student distribution

Add endpoint to create groups automatically

Deploy ClassHub API with Flask, JWT auth and Firebase integration

initial commit