fix: configure Flyway to use explicit PostgreSQL datasource

With two DataSource beans (PostgreSQL + ClickHouse), Flyway was picking
up the ClickHouse DataSource and failing with auth errors. Explicitly
configure Flyway's url/user/password to target PostgreSQL.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main/resources/application.yml

@@ -12,6 +12,9 @@ spring:
   flyway:
     enabled: true
     locations: classpath:db/migration
+    url: ${SPRING_DATASOURCE_URL:jdbc:postgresql://postgres:5432/cameleer_saas}
+    user: ${SPRING_DATASOURCE_USERNAME:cameleer}
+    password: ${SPRING_DATASOURCE_PASSWORD:cameleer_dev}
   security:
     oauth2:
       resourceserver: