Add word-book practice, iOS app shell, and fix embedded WebView blank screen.

Ship dual-track learning (daily accumulation vs textbook),沪教/商务词书 APIs and UI, native iOS wrapper with bundled H5, and production book import on deploy.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/routers/quiz_router.py

@@ -1,4 +1,6 @@
-from fastapi import APIRouter, Depends
+from typing import Literal, Optional
+
+from fastapi import APIRouter, Depends, Query
 from sqlalchemy.orm import Session
 
 from auth import get_current_user
@@ -17,19 +19,21 @@ router = APIRouter(prefix="/api/quiz", tags=["quiz"])
 
 @router.get("/daily", response_model=DailyQuizResponse)
 def daily_quiz(
+    track: Literal["accumulation", "book"] = Query("accumulation"),
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):
-    result = quiz_service.get_daily_quiz(db, current_user)
+    result = quiz_service.get_daily_quiz(db, current_user, track=track)
     return DailyQuizResponse(**result)
 
 
 @router.get("/spell", response_model=DailyQuizResponse)
 def spell_quiz(
+    track: Literal["accumulation", "book"] = Query("accumulation"),
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):
-    result = quiz_service.get_spell_quiz(db, current_user)
+    result = quiz_service.get_spell_quiz(db, current_user, track=track)
     return DailyQuizResponse(**result)
 
 
@@ -53,7 +57,8 @@ def submit_answer(
 
 @router.get("/stats", response_model=QuizStatsResponse)
 def quiz_stats(
+    track: Literal["accumulation", "book"] = Query("accumulation"),
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):
-    return quiz_service.get_stats(db, current_user)
+    return quiz_service.get_stats(db, current_user, track=track)