feat(backend): consolidation finale Spec 001 LCB-FT + Flyway V1-V5

Migrations Flyway (consolidées) :
- V1 : Schéma complet (69 tables, 1322 lignes)
- V2 : Colonnes BaseEntity (cree_par, modifie_par)
- V3 : Colonnes métier manquantes (adresses, alert_configuration)
- V4 : Correction system_logs (renommage colonnes, ajout timestamp)
- V5 : Nettoyage alert_configuration (suppression colonnes obsolètes)
- Suppression V2-V6 obsolètes (fragmentés)

Entités LCB-FT :
- AlerteLcbFt : Alertes anti-blanchiment
- AlertConfiguration : Configuration alertes
- SystemAlert : Alertes système
- SystemLog : Logs techniques (DÉJÀ COMMITÉE avec super.onCreate fix)

Services LCB-FT (T015, T016) :
- AlerteLcbFtService + Resource : Dashboard alertes admin
- AlertMonitoringService : Surveillance transactions
- SystemLoggingService : Logs centralisés
- FileStorageService : Upload documents

Repositories :
- AlerteLcbFtRepository
- AlertConfigurationRepository
- SystemAlertRepository
- SystemLogRepository

Tests :
- GlobalExceptionMapperTest : 17 erreurs corrigées (toResponse())

Spec 001 : 27/27 tâches (100%)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/main/java/dev/lions/unionflow/server/entity/SystemAlert.java

@@ -0,0 +1,118 @@
+package dev.lions.unionflow.server.entity;
+
+import jakarta.persistence.*;
+import lombok.Getter;
+import lombok.Setter;
+
+import java.time.LocalDateTime;
+
+/**
+ * Entité pour les alertes système.
+ * Enregistre les alertes de seuils dépassés, erreurs critiques, etc.
+ *
+ * @author UnionFlow Team
+ * @version 1.0
+ * @since 2026-03-15
+ */
+@Entity
+@Table(name = "system_alerts", indexes = {
+    @Index(name = "idx_system_alert_timestamp", columnList = "timestamp"),
+    @Index(name = "idx_system_alert_level", columnList = "level"),
+    @Index(name = "idx_system_alert_acknowledged", columnList = "acknowledged"),
+    @Index(name = "idx_system_alert_source", columnList = "source")
+})
+@Getter
+@Setter
+public class SystemAlert extends BaseEntity {
+
+    /**
+     * Niveau de l'alerte (CRITICAL, ERROR, WARNING, INFO)
+     */
+    @Column(name = "level", nullable = false, length = 20)
+    private String level;
+
+    /**
+     * Titre court de l'alerte
+     */
+    @Column(name = "title", nullable = false, length = 255)
+    private String title;
+
+    /**
+     * Message détaillé de l'alerte
+     */
+    @Column(name = "message", nullable = false, length = 1000)
+    private String message;
+
+    /**
+     * Date/heure de création de l'alerte
+     */
+    @Column(name = "timestamp", nullable = false)
+    private LocalDateTime timestamp;
+
+    /**
+     * Alerte acquittée ou non
+     */
+    @Column(name = "acknowledged", nullable = false)
+    private Boolean acknowledged = false;
+
+    /**
+     * Email de l'utilisateur ayant acquitté l'alerte
+     */
+    @Column(name = "acknowledged_by", length = 255)
+    private String acknowledgedBy;
+
+    /**
+     * Date/heure d'acquittement
+     */
+    @Column(name = "acknowledged_at")
+    private LocalDateTime acknowledgedAt;
+
+    /**
+     * Source de l'alerte (CPU, MEMORY, DISK, DATABASE, etc.)
+     */
+    @Column(name = "source", length = 100)
+    private String source;
+
+    /**
+     * Type d'alerte (THRESHOLD, INFO, ERROR, etc.)
+     */
+    @Column(name = "alert_type", length = 50)
+    private String alertType;
+
+    /**
+     * Valeur actuelle ayant déclenché l'alerte
+     */
+    @Column(name = "current_value")
+    private Double currentValue;
+
+    /**
+     * Valeur seuil dépassée
+     */
+    @Column(name = "threshold_value")
+    private Double thresholdValue;
+
+    /**
+     * Unité de mesure (%, MB, GB, ms, etc.)
+     */
+    @Column(name = "unit", length = 20)
+    private String unit;
+
+    /**
+     * Actions recommandées pour résoudre l'alerte
+     */
+    @Column(name = "recommended_actions", columnDefinition = "TEXT")
+    private String recommendedActions;
+
+    /**
+     * Initialisation automatique du timestamp
+     */
+    @PrePersist
+    protected void onCreate() {
+        if (timestamp == null) {
+            timestamp = LocalDateTime.now();
+        }
+        if (acknowledged == null) {
+            acknowledged = false;
+        }
+    }
+}