fix: pass credentials to Flyway when using separate datasource URL

When spring.flyway.url is set independently, Spring Boot does not
inherit credentials from spring.datasource. Add explicit user/password
to both application.yml and K8s deployment to prevent "no password"
failures on feature branch deployments.

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

cameleer3-server-app/src/main/resources/application.yml

@@ -11,6 +11,8 @@ spring:
     enabled: true
     locations: classpath:db/migration
     url: jdbc:postgresql://localhost:5432/cameleer3?currentSchema=${CAMELEER_DB_SCHEMA:public},public
+    user: ${spring.datasource.username}
+    password: ${spring.datasource.password}
     schemas: ${CAMELEER_DB_SCHEMA:public}
     default-schema: ${CAMELEER_DB_SCHEMA:public}
   mvc:

deploy/base/server.yaml

@@ -36,6 +36,16 @@ spec:
                 secretKeyRef:
                   name: postgres-credentials
                   key: POSTGRES_PASSWORD
+            - name: SPRING_FLYWAY_USER
+              valueFrom:
+                secretKeyRef:
+                  name: postgres-credentials
+                  key: POSTGRES_USER
+            - name: SPRING_FLYWAY_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: postgres-credentials
+                  key: POSTGRES_PASSWORD
             - name: OPENSEARCH_URL
               value: "http://opensearch.cameleer.svc.cluster.local:9200"
             - name: CAMELEER_OPENSEARCH_INDEX_PREFIX