feat: 接口字段补 @Schema 中文说明 + 精简冗余字段 + 接入 Prometheus 监控

- 全部 VO 字段补 @Schema(description) 中文说明，在线文档字段可读
- AppEpisodeVO 精简 duration/isFree 冗余字段（保留 durationSec/locked）
- framework 引入 actuator + micrometer-registry-prometheus
- SecurityConfig 放行 /actuator/prometheus，双服务配置 management 暴露指标
- 新增 deploy/docker-compose.yml + prometheus.yml 监控部署配置

deploy/prometheus.yml

@@ -0,0 +1,16 @@
+# Author: fruit.com.cn
+# Prometheus 抓取配置：抓取后端双服务的 actuator 指标
+global:
+  scrape_interval: 15s
+  evaluation_interval: 15s
+
+scrape_configs:
+  - job_name: "fruitshorts-app-api"
+    metrics_path: "/actuator/prometheus"
+    static_configs:
+      - targets: ["host.docker.internal:8081"]
+
+  - job_name: "fruitshorts-admin-api"
+    metrics_path: "/actuator/prometheus"
+    static_configs:
+      - targets: ["host.docker.internal:8080"]