fix(adaptive): 修复 429 计数归零写入及 reset 语义

- sql.rs: UPDATE 时对 concurrent_429_count / rpm_429_count 加 COALESCE(, 0)，避免 None 覆写为 NULL
- effects.rs: rpm_429_count 始终写入 Some(projection.rpm_429_count)，不再过滤零值；新增 unknown-429 场景下零值持久化的单元测试
- adaptive.rs: reset 接口将两个计数字段置为 Some(0) 而非 None，与数据库默认语义对齐；同步修正集成测试断言
- docker-compose.build.yml: 补充 AETHER_GATEWAY_AUTO_PREPARE_DATABASE 默认开启
- README.md: 同步说明 build compose 也已默认开启自动迁移

apps/aether-gateway/src/tests/control/admin/adaptive.rs

@@ -440,8 +440,8 @@ async fn gateway_resets_admin_adaptive_learning_locally_with_trusted_admin_princ
         .await
         .expect("repository query should succeed");
     assert_eq!(updated[0].learned_rpm_limit, None);
-    assert_eq!(updated[0].concurrent_429_count, None);
-    assert_eq!(updated[0].rpm_429_count, None);
+    assert_eq!(updated[0].concurrent_429_count, Some(0));
+    assert_eq!(updated[0].rpm_429_count, Some(0));
     assert_eq!(updated[0].adjustment_history, None);
 
     gateway_handle.abort();