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/db_migrate.py

@@ -32,6 +32,40 @@ def run_migrations() -> None:
                     )
                 )
 
+        if insp.has_table("user_settings"):
+            cols = {c["name"] for c in insp.get_columns("user_settings")}
+            if "active_book_id" not in cols:
+                conn.execute(text("ALTER TABLE user_settings ADD COLUMN active_book_id INTEGER"))
+
+        if not insp.has_table("user_book_settings"):
+            conn.execute(
+                text(
+                    """
+                    CREATE TABLE user_book_settings (
+                        id INTEGER PRIMARY KEY AUTO_INCREMENT,
+                        user_id INTEGER NOT NULL,
+                        book_id INTEGER NOT NULL,
+                        daily_target INTEGER NOT NULL DEFAULT 12,
+                        master_required_count INTEGER NOT NULL DEFAULT 3,
+                        weak_wrong_threshold INTEGER NOT NULL DEFAULT 2,
+                        CONSTRAINT uq_user_book_settings UNIQUE (user_id, book_id),
+                        FOREIGN KEY(user_id) REFERENCES users (id),
+                        FOREIGN KEY(book_id) REFERENCES word_books (id)
+                    )
+                    """
+                )
+            )
+
+        if insp.has_table("words"):
+            cols = {c["name"] for c in insp.get_columns("words")}
+            if "book_id" not in cols:
+                conn.execute(
+                    text("ALTER TABLE words ADD COLUMN book_id INTEGER NOT NULL DEFAULT 0")
+                )
+                conn.execute(text("CREATE INDEX ix_words_book_id ON words (book_id)"))
+            if "book_entry_id" not in cols:
+                conn.execute(text("ALTER TABLE words ADD COLUMN book_entry_id INTEGER"))
+
         if insp.has_table("words") and insp.has_table("quiz_records"):
             conn.execute(
                 text(