refactor(mp): 长轮询通用化 — useLongPolling hook + 咨询详情页接入

- 新增 useLongPolling hook：generation counter 防重叠、useDidShow/Hide 可见性控制、失败退避、enabled 守卫
- 患者端 + 医生端 consultation/detail 接入，删除约 80 行重复长轮询代码
- 架构建议 5/5 全部完成 ✅

apps/miniprogram/src/hooks/useLongPolling.ts

@@ -0,0 +1,93 @@
+import { useRef, useEffect } from 'react';
+import { useDidShow, useDidHide } from '@tarojs/taro';
+
+interface LongPollOptions<T> {
+  /** 轮询函数，返回新数据或 null/undefined */
+  pollFn: () => Promise<T | null | undefined>;
+  /** 收到新数据后的回调 */
+  onData: (data: T) => void;
+  /** 是否启用轮询（受外部状态控制） */
+  enabled: boolean;
+  /** 成功轮询间隔 ms，默认 3000 */
+  intervalMs?: number;
+  /** 连续失败上限，默认 50 */
+  maxFailures?: number;
+}
+
+/**
+ * 通用长轮询 hook。
+ *
+ * - generation counter 杜绝新旧循环重叠
+ * - useDidShow/useDidHide 控制页面可见性
+ * - 失败退避：delay = min(failCount * 2000, 30000)
+ * - 自动在 enabled 变 false 时停止（如会话关闭）
+ */
+export function useLongPolling<T>({
+  pollFn,
+  onData,
+  enabled,
+  intervalMs = 3000,
+  maxFailures = 50,
+}: LongPollOptions<T>) {
+  const generation = useRef(0);
+  const mountedRef = useRef(true);
+  const pollFnRef = useRef(pollFn);
+  const onDataRef = useRef(onData);
+  pollFnRef.current = pollFn;
+  onDataRef.current = onData;
+
+  const start = () => {
+    const gen = ++generation.current;
+    runPoll(gen, 0);
+  };
+
+  const stop = () => {
+    generation.current += 1;
+  };
+
+  const runPoll = async (gen: number, failCount: number) => {
+    if (gen !== generation.current || !mountedRef.current) return;
+    if (failCount >= maxFailures) return;
+    try {
+      const data = await pollFnRef.current();
+      if (gen !== generation.current || !mountedRef.current) return;
+      if (data != null) {
+        onDataRef.current(data);
+      }
+      failCount = 0;
+    } catch {
+      failCount++;
+    }
+    if (gen !== generation.current || !mountedRef.current) return;
+    const delay = failCount > 0 ? Math.min(failCount * 2000, 30000) : intervalMs;
+    await new Promise<void>((r) => setTimeout(r, delay));
+    if (gen === generation.current && mountedRef.current) {
+      runPoll(gen, failCount);
+    }
+  };
+
+  // enabled 变 false → 停止；变 true → 启动
+  useEffect(() => {
+    if (enabled) {
+      start();
+    } else {
+      stop();
+    }
+  }, [enabled]);
+
+  useDidShow(() => {
+    if (enabled) start();
+  });
+  useDidHide(() => {
+    stop();
+  });
+
+  useEffect(() => {
+    return () => {
+      generation.current += 1;
+      mountedRef.current = false;
+    };
+  }, []);
+
+  return { start, stop };
+}