Resolve merge conflicts for PR #25: customizable mobile reading experience

- Backend: Replace PR's Book-only models with main's full models
  (EBook, BookChapter, DownloadRecord, ReadingProgress, ReadingSettings)
- Backend: Add reader app (ReadingSettings model, serializer, view, URL)
- Frontend: Port reader feature files from web/ to frontend/ (api, hooks,
  components/reader/, pages/ReadingPage, types/reader, reader.css)
- Frontend: Add /read/:id route to App.tsx for chapter-based reading view
- All imports adjusted for frontend/src directory structure

frontend/src/api/reader.ts

@@ -0,0 +1,112 @@
+/**
+ * API client for the reader module — reading settings, chapters, and progress.
+ */
+
+import type {
+  ChapterDetail,
+  ChapterSummary,
+  ReadingProgress,
+  ReadingSettings,
+} from "../types/reader";
+
+const API_BASE = "/api";
+
+/**
+ * Fetch the current user's reading settings.
+ * Auto-creates defaults on the server if none exist.
+ */
+export async function getReadingSettings(): Promise<ReadingSettings> {
+  const response = await fetch(`${API_BASE}/reader/settings/`);
+  if (!response.ok) {
+    throw new Error(
+      `Failed to fetch reading settings: ${response.status} ${response.statusText}`
+    );
+  }
+  return response.json() as Promise<ReadingSettings>;
+}
+
+/**
+ * Update (full or partial) the user's reading settings.
+ */
+export async function updateReadingSettings(
+  settings: Partial<ReadingSettings>
+): Promise<ReadingSettings> {
+  const method = settings.theme !== undefined ? "PUT" : "PATCH";
+  const response = await fetch(`${API_BASE}/reader/settings/`, {
+    method,
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(settings),
+  });
+  if (!response.ok) {
+    throw new Error(
+      `Failed to update reading settings: ${response.status} ${response.statusText}`
+    );
+  }
+  return response.json() as Promise<ReadingSettings>;
+}
+
+/**
+ * Fetch the table of contents (chapter list) for a book.
+ */
+export async function getChapters(bookId: number): Promise<ChapterSummary[]> {
+  const response = await fetch(`${API_BASE}/books/${bookId}/chapters/`);
+  if (!response.ok) {
+    throw new Error(
+      `Failed to fetch chapters: ${response.status} ${response.statusText}`
+    );
+  }
+  return response.json() as Promise<ChapterSummary[]>;
+}
+
+/**
+ * Fetch a specific chapter with full content for reading.
+ */
+export async function getChapterContent(
+  bookId: number,
+  chapterNumber: number
+): Promise<ChapterDetail> {
+  const response = await fetch(
+    `${API_BASE}/books/${bookId}/chapters/${chapterNumber}/`
+  );
+  if (!response.ok) {
+    throw new Error(
+      `Failed to fetch chapter ${chapterNumber}: ${response.status} ${response.statusText}`
+    );
+  }
+  return response.json() as Promise<ChapterDetail>;
+}
+
+/**
+ * Fetch reading progress for a book.
+ */
+export async function getReadingProgress(
+  bookId: number
+): Promise<ReadingProgress> {
+  const response = await fetch(`${API_BASE}/books/${bookId}/progress/`);
+  if (!response.ok) {
+    throw new Error(
+      `Failed to fetch reading progress: ${response.status} ${response.statusText}`
+    );
+  }
+  return response.json() as Promise<ReadingProgress>;
+}
+
+/**
+ * Update reading progress for a book.
+ */
+export async function updateReadingProgress(
+  bookId: number,
+  progress: Partial<ReadingProgress>
+): Promise<ReadingProgress> {
+  const response = await fetch(`${API_BASE}/books/${bookId}/progress/`, {
+    method: "PUT",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(progress),
+  });
+  if (!response.ok) {
+    throw new Error(
+      `Failed to update reading progress: ${response.status} ${response.statusText}`
+    );
+  }
+  return response.json() as Promise<ReadingProgress>;
+}