fix: include wait-for-db.sh in Docker build context

The .dockerignore added in 8a0d82f incorrectly excluded wait-for-db.sh,
but the Dockerfile copies it as the container entrypoint. This caused
the Docker build to fail with 'failed to compute cache key: not found'.

Quality gates: verified file exists, py_compile passed.

apps/api/src/models/user_config.py

@@ -14,8 +14,12 @@ if TYPE_CHECKING:
 class UserConfig(UUIDPrimaryKeyMixin, TimestampMixin, Base):
     __tablename__ = "user_configs"
 
-    user_id: Mapped[uuid.UUID] = mapped_column(UUID(), ForeignKey("users.id"), nullable=False, unique=True)
-    config: Mapped[dict[str, object]] = mapped_column(JSON, default=dict, nullable=False)
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(), ForeignKey("users.id"), nullable=False, unique=True
+    )
+    config: Mapped[dict[str, object]] = mapped_column(
+        JSON, default=dict, nullable=False
+    )
 
     user: Mapped["User"] = relationship(back_populates="user_config")