fix(backend): explicit Flyway bean to bypass broken auto-configuration

Spring Boot 4.0 Flyway auto-configuration is not triggering in the CI
environment — confirmed by empty DB and no flyway_schema_history table.
Replace YAML-based auto-config with an explicit @Bean that creates and
runs Flyway directly on startup, independent of any auto-configuration
conditions. Disable the auto-config via spring.flyway.enabled=false to
prevent interference. Add @DependsOn("flyway") to DataInitializer to
enforce that CommandLineRunner beans are only registered after migrations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/config/DataInitializer.java

@@ -4,6 +4,7 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
 import org.raddatz.familienarchiv.model.AppUser;
+import org.springframework.context.annotation.DependsOn;
 import org.raddatz.familienarchiv.model.Document;
 import org.raddatz.familienarchiv.model.DocumentStatus;
 import org.raddatz.familienarchiv.model.Person;
@@ -27,6 +28,7 @@ import java.util.Set;
 @Configuration
 @RequiredArgsConstructor
 @Slf4j
+@DependsOn("flyway")
 public class DataInitializer {
 
     @Value("${app.admin.username:admin}")

backend/src/main/java/org/raddatz/familienarchiv/config/FlywayConfig.java

@@ -0,0 +1,29 @@
+package org.raddatz.familienarchiv.config;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.flywaydb.core.Flyway;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import javax.sql.DataSource;
+
+@Configuration
+@RequiredArgsConstructor
+@Slf4j
+public class FlywayConfig {
+
+    private final DataSource dataSource;
+
+    @Bean(name = "flyway")
+    public Flyway flyway() {
+        log.info("Running Flyway migrations...");
+        Flyway flyway = Flyway.configure()
+                .dataSource(dataSource)
+                .locations("classpath:db/migration")
+                .load();
+        var result = flyway.migrate();
+        log.info("Flyway: {} migration(s) applied.", result.migrationsExecuted);
+        return flyway;
+    }
+}

backend/src/main/resources/application.yaml

@@ -9,11 +9,7 @@ spring:
     driver-class-name: org.postgresql.Driver
 
   flyway:
-    enabled: true
-    locations: classpath:db/migration
-    url: ${SPRING_DATASOURCE_URL}
-    user: ${SPRING_DATASOURCE_USERNAME}
-    password: ${SPRING_DATASOURCE_PASSWORD}
+    enabled: false  # Managed explicitly via FlywayConfig bean
 
   jpa:
     hibernate: