feat(notify): 站内通知与手工开单，指派/改状态/评论/验收都有人收到

M2 最后一块：让"该我办了"能出现在系统里，并且允许不经过任务直接开单。

通知（backend/app/services/notify.py 统一出口）
- 七类触发：task_assigned、task_status_changed、item_commented、
  ticket_assigned、ticket_submitted、ticket_approved/rejected、task_unblocked
- 不通知自己：notify() 按 actor_id 跳过，调用方不用各自判断
- 已读：GET /notifications、/unread-count、POST /read、/read-all

手工开单
- POST /tickets：直接指定人、初始 open，与任务升级单共用同一条 kind='ticket' item，
  ticket_ext.parent_item_id 为空，验收通过不回流任务
- 指派前 _ensure_member 校验在册成员，越界指派返回 1001（避免"挂在看不到的名字上"）

前端
- Web：通知页 /w/:wsId/notifications（未读/全部，点开标已读并跳目标）；
  工单页"新建"面板；AppShell 每 30 秒对未读数，标已读后 dispatch notifications:changed 立刻刷新；
  任务与工单支持 ?open= 深链落地即展开
- 安卓：五个 tab 加"通知"，未读数 30 秒刷新；工单动作按需求人/办理人/管理员显隐；手工开单对话框

验证
- pytest 85 passed（新增 backend/tests/test_notifications.py 6 个用例）
- ruff check / format --check 全 0
- tsc --noEmit 通过；vite build 成功
- web/e2e/notifications.mjs 12 项断言全绿（手工开单 → B 收到 → 点开跳转 → 未读归零）
- 安卓：本机 JDK 25 与 Gradle 8.7 / AGP 8.7.3 不兼容，本次未做编译验证，
  装回 JDK 17 后第一件事是 assembleDebug

web/src/pages/Notifications.tsx

@@ -0,0 +1,228 @@
+import { useCallback, useEffect, useMemo, useState } from "react";
+import { useNavigate, useParams } from "react-router-dom";
+
+import { AppShell } from "../components/AppShell";
+import { Bell, Check, TicketIcon, Inbox, Clock } from "../components/icons";
+import { Button, EmptyState, PageHeader, SkeletonRows } from "../components/ui";
+import { api, ApiError } from "../lib/client";
+import type { AppNotification } from "../lib/types";
+
+const PAGE = 30;
+
+/** 工单类通知点开跳到工单页，其余回任务页——都带 `?open=`，落地即展开那一条。 */
+function targetOf(wsId: string, n: AppNotification): string {
+  if (!n.item_id) return `/w/${wsId}/notifications`;
+  const isTicket = n.kind.startsWith("ticket_");
+  return isTicket ? `/w/${wsId}/tickets?open=${n.item_id}` : `/w/${wsId}?open=${n.item_id}`;
+}
+
+function iconOf(kind: string) {
+  if (kind.startsWith("ticket_")) return <TicketIcon size={15} />;
+  if (kind === "item_commented") return <Inbox size={15} />;
+  return <Bell size={15} />;
+}
+
+function ago(iso: string): string {
+  const then = new Date(iso).getTime();
+  const diff = Math.max(0, Date.now() - then);
+  const min = Math.floor(diff / 60_000);
+  if (min < 1) return "刚刚";
+  if (min < 60) return `${min} 分钟前`;
+  const hour = Math.floor(min / 60);
+  if (hour < 24) return `${hour} 小时前`;
+  const day = Math.floor(hour / 24);
+  if (day < 30) return `${day} 天前`;
+  return new Date(iso).toLocaleDateString("zh-CN");
+}
+
+/** 通知页：默认只看未读——"全部"是查历史用的，不是日常入口。 */
+export function NotificationsPage() {
+  const { wsId = "" } = useParams();
+  const navigate = useNavigate();
+  const [tab, setTab] = useState<"unread" | "all">("unread");
+  const [rows, setRows] = useState<AppNotification[]>([]);
+  const [cursor, setCursor] = useState<string | null>(null);
+  const [hasMore, setHasMore] = useState(false);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  const load = useCallback(
+    async (reset: boolean) => {
+      setLoading(true);
+      setError(null);
+      try {
+        const params = new URLSearchParams({
+          unread_only: tab === "unread" ? "true" : "false",
+          limit: String(PAGE),
+        });
+        if (!reset && cursor) params.set("cursor", cursor);
+        const page = await api.get<{
+          notifications: AppNotification[];
+          next_cursor: string | null;
+          has_more: boolean;
+        }>(`/workspaces/${wsId}/notifications?${params.toString()}`);
+        setRows((prev) => (reset ? page.notifications : [...prev, ...page.notifications]));
+        setCursor(page.next_cursor);
+        setHasMore(page.has_more);
+      } catch (err) {
+        setError(err instanceof ApiError ? err.message : "通知加载失败");
+      } finally {
+        setLoading(false);
+      }
+    },
+    [wsId, tab, cursor],
+  );
+
+  useEffect(() => {
+    setRows([]);
+    setCursor(null);
+    void load(true);
+    // 只在切 tab / 换工作区时重拉，翻页由按钮触发
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [wsId, tab]);
+
+  const unreadCount = useMemo(() => rows.filter((r) => !r.read_at).length, [rows]);
+
+  async function markRead(n: AppNotification) {
+    if (!n.read_at) {
+      try {
+        await api.post(`/workspaces/${wsId}/notifications/${n.id}/read`);
+      } catch {
+        /* 标已读失败不拦着用户点进去看 */
+      }
+      setRows((prev) =>
+        prev.map((r) => (r.id === n.id ? { ...r, read_at: new Date().toISOString() } : r)),
+      );
+      window.dispatchEvent(new Event("notifications:changed"));
+    }
+    navigate(targetOf(wsId, n));
+  }
+
+  async function markAll() {
+    try {
+      await api.post(`/workspaces/${wsId}/notifications/read-all`);
+      setRows((prev) => prev.map((r) => ({ ...r, read_at: r.read_at ?? new Date().toISOString() })));
+      window.dispatchEvent(new Event("notifications:changed"));
+    } catch (err) {
+      setError(err instanceof ApiError ? err.message : "操作失败");
+    }
+  }
+
+  return (
+    <AppShell wsId={wsId} active="notifications">
+      <PageHeader
+        eyebrow="事情有动静时，这里会告诉你"
+        title="通知"
+        desc="工单被接受、提交、验收，任务被指派、改状态，有人在你关注的事情下说话，都会落在这里。"
+        actions={
+          <>
+            <Button variant="ghost" size="sm" onClick={() => void load(true)} disabled={loading}>
+              刷新
+            </Button>
+            <Button variant="subtle" size="sm" onClick={() => void markAll()} disabled={!unreadCount}>
+              全部已读
+            </Button>
+          </>
+        }
+      />
+
+      <div className="mb-3 flex items-center gap-1">
+        {(
+          [
+            ["unread", "未读"],
+            ["all", "全部"],
+          ] as const
+        ).map(([key, label]) => (
+          <button
+            key={key}
+            onClick={() => setTab(key)}
+            className={`rounded-lg px-3 py-1.5 text-xs transition ${
+              tab === key
+                ? "bg-ink-900 font-medium text-white"
+                : "text-ink-500 hover:bg-ink-100 hover:text-ink-800"
+            }`}
+          >
+            {label}
+          </button>
+        ))}
+        {tab === "unread" && unreadCount > 0 ? (
+          <span className="ml-auto text-2xs text-ink-400">还有 {unreadCount} 条没看</span>
+        ) : null}
+      </div>
+
+      {error ? (
+        <div className="mb-3 rounded-xl border border-rust-100 bg-rust-50 px-4 py-3 text-sm text-rust-700">
+          {error}
+        </div>
+      ) : null}
+
+      {loading && rows.length === 0 ? (
+        <SkeletonRows rows={4} />
+      ) : rows.length === 0 ? (
+        <div className="card">
+          <EmptyState
+            icon={<Bell size={20} />}
+            title={tab === "unread" ? "没有未读通知" : "还没有通知"}
+            hint={
+              tab === "unread"
+                ? "有人给你派活、或你关注的事情有进展时，会出现在这里。"
+                : "这里会留下所有历史通知，方便回头找。"
+            }
+          />
+        </div>
+      ) : (
+        <ul className="space-y-2">
+          {rows.map((n) => (
+            <li key={n.id} className={`card ${n.read_at ? "" : "border-primary-100 bg-primary-50/40"}`}>
+              <button
+                onClick={() => void markRead(n)}
+                className="flex w-full items-start gap-3 px-4 py-3 text-left"
+              >
+                <span
+                  className={`mt-0.5 grid h-7 w-7 shrink-0 place-items-center rounded-full ${
+                    n.read_at ? "bg-ink-100 text-ink-500" : "bg-primary-500 text-white"
+                  }`}
+                >
+                  {iconOf(n.kind)}
+                </span>
+                <span className="min-w-0 flex-1">
+                  <span className="flex items-baseline gap-2">
+                    <span className="truncate text-sm font-medium text-ink-900">{n.title}</span>
+                    {!n.read_at ? (
+                      <span className="h-1.5 w-1.5 shrink-0 rounded-full bg-clay-500" />
+                    ) : null}
+                    <span className="ml-auto shrink-0 text-2xs text-ink-400">
+                      {ago(n.created_at)}
+                    </span>
+                  </span>
+                  {n.body ? (
+                    <span className="mt-1 block truncate text-xs text-ink-500">{n.body}</span>
+                  ) : null}
+                  {n.item_title ? (
+                    <span className="mt-1.5 inline-flex items-center gap-1 text-2xs text-ink-400">
+                      <Clock size={11} />
+                      {n.item_title}
+                    </span>
+                  ) : null}
+                </span>
+              </button>
+            </li>
+          ))}
+        </ul>
+      )}
+
+      {hasMore ? (
+        <div className="mt-4 flex justify-center">
+          <Button variant="ghost" size="sm" onClick={() => void load(false)} disabled={loading}>
+            加载更早
+          </Button>
+        </div>
+      ) : rows.length > 0 && !hasMore ? (
+        <p className="mt-4 text-center text-2xs text-ink-300">
+          <Check size={11} className="mr-1 inline" />
+          没有更多了
+        </p>
+      ) : null}
+    </AppShell>
+  );
+}