feat(portal-shell): extract domain API layer and migrate 31 widgets

Task 4-10 of portal-shell data abstraction plan (M1-M2).

Add 7 domain API modules under src/lib/api/ (parent/admin/teacher/
student/universal/sidebar/topbar), each exposing semantic hooks that
wrap useWidgetQuery/useWidgetMutation and return flattened domain
models. Widget code now imports from @/lib/api instead of inlining
gql literals.

- 31 widgets migrated (gql literal count in widgets: 0)
- 7 test files (85 cases, all passing)
- topbar.useNotifications renamed to useNotificationBell to avoid
  barrel export collision with universal.useNotifications
- typecheck + lint (0 errors) + test (85/85) verified

apps/portal-shell/src/widgets/teacher/textbook-manager/index.tsx

@@ -0,0 +1,129 @@
+"use client";
+
+/**
+ * textbook-manager（teacher / main）
+ *
+ * 教材管理：按科目与年级筛选教材，点击教材查看章节列表。
+ * 通过 useWidgetQuery 查询 apollo-router → content 子图的 textbooks 数据。
+ *
+ * 关联：portal-shell spec §5.6 统一 Hook
+ */
+import { useState } from "react";
+import { useTextbooks } from "@/lib/api";
+import { PluginSkeleton } from "@/shell/PluginLoader";
+import type { PluginProps } from "@/lib/types";
+
+export default function TextbookManager(
+  _props: PluginProps,
+): React.ReactElement {
+  const [subjectInput, setSubjectInput] = useState("");
+  const [gradeInput, setGradeInput] = useState("");
+  const [appliedSubject, setAppliedSubject] = useState("");
+  const [appliedGrade, setAppliedGrade] = useState("");
+  const [selectedId, setSelectedId] = useState<string | null>(null);
+
+  const { data, loading } = useTextbooks({
+    subjectId: appliedSubject || undefined,
+    grade: appliedGrade || undefined,
+  });
+
+  if (loading && !data) {
+    return <PluginSkeleton variant="list" />;
+  }
+
+  const textbooks = data ?? [];
+  const selected = textbooks.find((t) => t.id === selectedId) ?? null;
+
+  const handleApply = (): void => {
+    setAppliedSubject(subjectInput.trim());
+    setAppliedGrade(gradeInput.trim());
+    setSelectedId(null);
+  };
+
+  return (
+    <section className="rounded-card border border-rule bg-surface p-md">
+      <h3 className="text-heading-3 text-ink">教材管理</h3>
+
+      <div className="mt-sm flex gap-md">
+        <label className="flex flex-col space-y-xs">
+          <span className="text-small text-ink-muted">科目 ID</span>
+          <input
+            type="text"
+            value={subjectInput}
+            onChange={(e) => setSubjectInput(e.target.value)}
+            className="rounded-button border border-rule bg-surface px-sm py-xs text-small text-ink"
+            placeholder="可选，输入科目 ID"
+          />
+        </label>
+        <label className="flex flex-col space-y-xs">
+          <span className="text-small text-ink-muted">年级</span>
+          <input
+            type="text"
+            value={gradeInput}
+            onChange={(e) => setGradeInput(e.target.value)}
+            className="rounded-button border border-rule bg-surface px-sm py-xs text-small text-ink"
+            placeholder="可选，如：三年级"
+          />
+        </label>
+        <button
+          type="button"
+          onClick={handleApply}
+          className="self-end rounded-button bg-accent px-md py-xs text-small text-ink-onAccent"
+        >
+          筛选
+        </button>
+      </div>
+
+      <div className="mt-md flex gap-md">
+        <ul className="flex-1 space-y-sm">
+          {textbooks.length === 0 ? (
+            <li className="text-small text-ink-muted">暂无教材数据</li>
+          ) : (
+            textbooks.map((t) => (
+              <li key={t.id}>
+                <button
+                  type="button"
+                  onClick={() => setSelectedId(t.id)}
+                  className={
+                    selectedId === t.id
+                      ? "w-full rounded-button border border-rule bg-subtle p-sm text-left"
+                      : "w-full rounded-button border border-rule bg-surface p-sm text-left"
+                  }
+                >
+                  <p className="text-body text-ink">{t.title}</p>
+                  <p className="text-small text-ink-muted">
+                    {t.author} · {t.publisher}
+                  </p>
+                  <p className="text-tiny text-ink-muted">ISBN: {t.isbn}</p>
+                </button>
+              </li>
+            ))
+          )}
+        </ul>
+
+        <div className="flex-1">
+          {selected ? (
+            <div className="rounded-card border border-rule bg-surface p-md">
+              <h4 className="text-body text-ink">{selected.title}</h4>
+              <p className="mt-xs text-small text-ink-muted">
+                {selected.author} · {selected.publisher}
+              </p>
+              <h5 className="mt-md text-small text-ink">章节列表</h5>
+              <ol className="mt-xs space-y-xs">
+                {selected.chapters.map((c, i) => (
+                  <li key={c.id} className="text-small text-ink">
+                    {i + 1}. {c.title}
+                  </li>
+                ))}
+              </ol>
+            </div>
+          ) : (
+            <div className="rounded-card border border-rule bg-surface p-md text-small text-ink-muted">
+              点击左侧教材查看章节
+            </div>
+          )}
+        </div>
+      </div>
+    </section>
+  );
+}