Fix flyway migration and use h2 in unit tests.

backend/src/test/resources/application-test.yml

@@ -1,10 +1,21 @@
 spring:
   datasource:
-    url: jdbc:postgresql://localhost:5432/your_test_database
-    username: test_user
-    password: test_password
+    url: jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE;MODE=PostgreSQL
+    username: sa
+    password: 
+    driver-class-name: org.h2.Driver
+  
+  h2:
+    console:
+      enabled: true
+  
+  jpa:
+    hibernate:
+      ddl-auto: none  # Let Flyway handle schema creation
+    show-sql: true
+    database-platform: org.hibernate.dialect.H2Dialect
   
   flyway:
     enabled: true
     clean-disabled: false  # Allow clean in tests
-    locations: classpath:db/migration
+    locations: classpath:db/migration