Deploy SQL Server with pre-installed DB using Docker

Question

I have created a docker image of SQL Server that includes a restored backup of an empty DB using the following dockerfile:

FROM mcr.microsoft.com/mssql/server:2019-latest AS build
ENV ACCEPT_EULA=Y
ENV SA_PASSWORD=myP@ss0rd#
ENV MSSQL_PID=Express

# Have a stage specifically to populate the data directory
FROM build AS data
WORKDIR /tmp
COPY TiPS_v.1.3.4.0.bak .
COPY restore-backup.sql .

RUN /opt/mssql/bin/sqlservr --accept-eula & sleep 10 \
    && /opt/mssql-tools/bin/sqlcmd -S localhost -U SA -P "myP@ss0rd#" -i /tmp/restore-backup.sql \
    && pkill sqlservr

# Final stage that actually will actually be run.   
FROM build AS release
# Copy the prepopulated data tree, but not the backup file
COPY --from=data /var/opt/mssql/data /var/opt/mssql/data    

Running a docker container off of that image works fine and I can access the restored DB. But when I try to run using docker-compose with following yml file:

version: '3'
services:
  mssql:
    image: tips-db:1.3.4.1
    container_name: "mssql-tips"
    user: root
    restart: always
    environment:
      ACCEPT_EULA: Y
    volumes:
      - ./mssql/data/:/var/opt/mssql/data
      - ./mssql/log/:/var/opt/mssql/log
      - ./mssql/secrets/:/var/opt/mssql/secrets   
    ports:
      - 11433:1433 

the restored DB is not there anymore. Only system databases are present.

I have only basic understanding of docker. I really can't understand why the .mdf, .ldf files of my Db are not persisted when then container is run. I can only see the files from system databases inside my local mssql/data folder.

Is there something I could do so that my restored DB is persisted after the container is run through docker-compose?