feat: Intégration du backend NestJS depuis YNOV

- Framework: NestJS avec TypeORM
- Authentification: JWT (access + refresh tokens)
- Gestion utilisateurs: CRUD complet avec validation
- Routes: auth, users, parents, assistantes maternelles
- Dockerfile pour conteneurisation

backend/src/entities/avenants_contrats.entity.ts

@@ -0,0 +1,42 @@
+import { Column, CreateDateColumn, Entity, JoinColumn, ManyToOne, PrimaryGeneratedColumn, UpdateDateColumn } from "typeorm";
+import { Contrat } from "./contrats.entity";
+import { Users } from "./users.entity";
+
+export enum StatutAvenantType {
+    PROPOSE = 'propose',
+    ACCEPTE = 'accepte',
+    REFUSE = 'refuse',
+}
+
+@Entity('avenants_contrats')
+export class AvenantContrat {
+    // Define your columns and relationships here
+    @PrimaryGeneratedColumn('uuid')
+    id: string;
+
+    @ManyToOne(() => Contrat, { onDelete: 'CASCADE' })
+    @JoinColumn({ name: 'id_contrat' })
+    contrat: Contrat;
+
+    @Column({ type: 'jsonb', nullable: true, name: 'modifications' })
+    modifications?: any;
+
+    @ManyToOne(() => Users, { nullable: true })
+    @JoinColumn({ name: 'initie_par', referencedColumnName: 'id' })
+    initiator?: Users;
+
+    @Column({
+        type: 'enum',
+        enum: StatutAvenantType,
+        enumName: 'statut_avenant_type',
+        default: StatutAvenantType.PROPOSE,
+        name: 'statut'
+    })
+    statut: StatutAvenantType;
+
+    @CreateDateColumn({ name: 'cree_le', type: 'timestamptz' })
+    createdAt: Date;
+
+    @UpdateDateColumn({ name: 'modifie_le', type: 'timestamptz' })
+    updatedAt: Date;
+}