feat(mobile): Implement Keycloak WebView authentication with HTTP callback

- Replace flutter_appauth with custom WebView implementation to resolve deep link issues
- Add KeycloakWebViewAuthService with integrated WebView for seamless authentication
- Configure Android manifest for HTTP cleartext traffic support
- Add network security config for development environment (192.168.1.11)
- Update Keycloak client to use HTTP callback endpoint (http://192.168.1.11:8080/auth/callback)
- Remove obsolete keycloak_auth_service.dart and temporary scripts
- Clean up dependencies and regenerate injection configuration
- Tested successfully on multiple Android devices (Xiaomi 2201116TG, SM A725F)

BREAKING CHANGE: Authentication flow now uses WebView instead of external browser
- Users will see Keycloak login page within the app instead of browser redirect
- Resolves ERR_CLEARTEXT_NOT_PERMITTED and deep link state management issues
- Maintains full OIDC compliance with PKCE flow and secure token storage

Technical improvements:
- WebView with custom navigation delegate for callback handling
- Automatic token extraction and user info parsing from JWT
- Proper error handling and user feedback
- Consistent authentication state management across app lifecycle

unionflow-mobile-apps/lib/core/models/evenement_model.g.dart

@@ -0,0 +1,94 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'evenement_model.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+EvenementModel _$EvenementModelFromJson(Map<String, dynamic> json) =>
+    EvenementModel(
+      id: json['id'] as String?,
+      titre: json['titre'] as String,
+      description: json['description'] as String?,
+      dateDebut: DateTime.parse(json['dateDebut'] as String),
+      dateFin: json['dateFin'] == null
+          ? null
+          : DateTime.parse(json['dateFin'] as String),
+      lieu: json['lieu'] as String?,
+      adresse: json['adresse'] as String?,
+      typeEvenement: $enumDecode(_$TypeEvenementEnumMap, json['typeEvenement']),
+      statut: $enumDecode(_$StatutEvenementEnumMap, json['statut']),
+      capaciteMax: (json['capaciteMax'] as num?)?.toInt(),
+      prix: (json['prix'] as num?)?.toDouble(),
+      inscriptionRequise: json['inscriptionRequise'] as bool,
+      dateLimiteInscription: json['dateLimiteInscription'] == null
+          ? null
+          : DateTime.parse(json['dateLimiteInscription'] as String),
+      instructionsParticulieres: json['instructionsParticulieres'] as String?,
+      contactOrganisateur: json['contactOrganisateur'] as String?,
+      materielRequis: json['materielRequis'] as String?,
+      visiblePublic: json['visiblePublic'] as bool,
+      actif: json['actif'] as bool,
+      creePar: json['creePar'] as String?,
+      dateCreation: json['dateCreation'] == null
+          ? null
+          : DateTime.parse(json['dateCreation'] as String),
+      modifiePar: json['modifiePar'] as String?,
+      dateModification: json['dateModification'] == null
+          ? null
+          : DateTime.parse(json['dateModification'] as String),
+      organisationId: json['organisationId'] as String?,
+      organisateurId: json['organisateurId'] as String?,
+    );
+
+Map<String, dynamic> _$EvenementModelToJson(EvenementModel instance) =>
+    <String, dynamic>{
+      'id': instance.id,
+      'titre': instance.titre,
+      'description': instance.description,
+      'dateDebut': instance.dateDebut.toIso8601String(),
+      'dateFin': instance.dateFin?.toIso8601String(),
+      'lieu': instance.lieu,
+      'adresse': instance.adresse,
+      'typeEvenement': _$TypeEvenementEnumMap[instance.typeEvenement]!,
+      'statut': _$StatutEvenementEnumMap[instance.statut]!,
+      'capaciteMax': instance.capaciteMax,
+      'prix': instance.prix,
+      'inscriptionRequise': instance.inscriptionRequise,
+      'dateLimiteInscription':
+          instance.dateLimiteInscription?.toIso8601String(),
+      'instructionsParticulieres': instance.instructionsParticulieres,
+      'contactOrganisateur': instance.contactOrganisateur,
+      'materielRequis': instance.materielRequis,
+      'visiblePublic': instance.visiblePublic,
+      'actif': instance.actif,
+      'creePar': instance.creePar,
+      'dateCreation': instance.dateCreation?.toIso8601String(),
+      'modifiePar': instance.modifiePar,
+      'dateModification': instance.dateModification?.toIso8601String(),
+      'organisationId': instance.organisationId,
+      'organisateurId': instance.organisateurId,
+    };
+
+const _$TypeEvenementEnumMap = {
+  TypeEvenement.assembleeGenerale: 'ASSEMBLEE_GENERALE',
+  TypeEvenement.reunion: 'REUNION',
+  TypeEvenement.formation: 'FORMATION',
+  TypeEvenement.conference: 'CONFERENCE',
+  TypeEvenement.atelier: 'ATELIER',
+  TypeEvenement.seminaire: 'SEMINAIRE',
+  TypeEvenement.evenementSocial: 'EVENEMENT_SOCIAL',
+  TypeEvenement.manifestation: 'MANIFESTATION',
+  TypeEvenement.celebration: 'CELEBRATION',
+  TypeEvenement.autre: 'AUTRE',
+};
+
+const _$StatutEvenementEnumMap = {
+  StatutEvenement.planifie: 'PLANIFIE',
+  StatutEvenement.confirme: 'CONFIRME',
+  StatutEvenement.enCours: 'EN_COURS',
+  StatutEvenement.termine: 'TERMINE',
+  StatutEvenement.annule: 'ANNULE',
+  StatutEvenement.reporte: 'REPORTE',
+};