feat: US #32 Section-based Reading Recommendations

Backend:
- Add ReadingSchedule and MeetingSection models for ebook reading schedules
- Implement recommendation algorithm: greedy partition minimizing per-meeting time variance
- Algorithm respects chapter boundaries, estimates time based on chapter weight
- Add serializers for schedules (list/detail/generate/confirm/update)
- Add ScheduleViewSet with endpoints: list, create (generate), retrieve, regenerate, confirm, update_meeting, reorder_meetings
- Add URL routes for /api/books/schedules/
- Create migration 0004 for new models

Frontend:
- Add types: MeetingSection, ReadingSchedule, GenerateRecommendationsRequest
- Add schedulesApi with methods: getSchedules, generateRecommendations, confirmSchedule, updateMeeting, reorderMeetings, deleteSchedule
- Build RecommendationPage with 4-column meeting layout, drag-and-drop chapter reassignment, generate/regenerate/confirm flow
- Add 'Schedule Reading' menu item to BookContextMenu
- Add route: /books/:ebookId/schedule

frontend/src/components/BookContextMenu.tsx

@@ -1,4 +1,5 @@
 import { useEffect, useLayoutEffect, useRef, useState } from "react";
+import { useNavigate } from "react-router-dom";
 import { useTranslation } from "react-i18n-lite";
 import { booksApi } from "../api/books";
 import { getApiErrorMessage } from "../api/errors";
@@ -46,6 +47,7 @@ export function BookContextMenu({
   const { t, language } = useTranslation();
   const locale = language as SupportedLanguage;
   const { showToast } = useToast();
+  const navigate = useNavigate();
   const menuRef = useRef<HTMLDivElement>(null);
   const [position, setPosition] = useState({ left: x, top: y });
   const [activeAction, setActiveAction] = useState<ActionKind>(null);
@@ -148,6 +150,18 @@ export function BookContextMenu({
       >
         {activeAction === "sync" ? t("contextMenu.syncingMetadata") : t("contextMenu.syncMetadata")}
       </button>
+      <button
+        type="button"
+        className={styles.item}
+        role="menuitem"
+        disabled={busy}
+        onClick={() => {
+          navigate(`/books/${book.id}/schedule`);
+          onClose();
+        }}
+      >
+        📅 Schedule Reading
+      </button>
       <div className={styles.separator} role="separator" />
       <button
         type="button"