refactor: rename canto-backend → backend, canto-frontend → frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/db/database.py

@@ -0,0 +1,53 @@
+from sqlalchemy import create_engine, event
+from sqlalchemy.orm import sessionmaker, declarative_base
+from sqlalchemy.pool import NullPool
+
+from config import settings
+
+_is_sqlite = "sqlite" in settings.DATABASE_URL
+
+engine = create_engine(
+    settings.DATABASE_URL,
+    connect_args={"check_same_thread": False} if _is_sqlite else {},
+    poolclass=NullPool if _is_sqlite else None,
+)
+
+if _is_sqlite:
+    @event.listens_for(engine, "connect")
+    def _set_wal(dbapi_conn, _):
+        dbapi_conn.execute("PRAGMA journal_mode=WAL")
+        dbapi_conn.execute("PRAGMA synchronous=NORMAL")
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+Base = declarative_base()
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+def init_db():
+    Base.metadata.create_all(bind=engine)
+    if "sqlite" in str(engine.url):
+        with engine.connect() as conn:
+            try:
+                conn.execute(__import__("sqlalchemy").text(
+                    "ALTER TABLE audiobook_characters ADD COLUMN gender VARCHAR(20)"
+                ))
+                conn.commit()
+            except Exception:
+                pass
+            for col_def in [
+                "ALTER TABLE audiobook_segments ADD COLUMN emo_text VARCHAR(20)",
+                "ALTER TABLE audiobook_segments ADD COLUMN emo_alpha REAL",
+                "ALTER TABLE audiobook_projects ADD COLUMN script_config JSON",
+                "ALTER TABLE users ADD COLUMN can_use_nsfw BOOLEAN DEFAULT FALSE NOT NULL",
+            ]:
+                try:
+                    conn.execute(__import__("sqlalchemy").text(col_def))
+                    conn.commit()
+                except Exception:
+                    pass