Rebuild Docker images with the latest security updates from time to time

**User Story**

As a node operator I want my containers to be kept up to date with the latest security updates so that I would be happier.

https://pythonspeed.com/articles/security-updates-in-docker/
https://stackoverflow.com/questions/26423515/how-to-automatically-update-your-docker-containers-if-base-images-are-updated

**Impacts**
Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.
- [ ] API (the application programming interface)
- [x] Build (the build process or something prior to compiled code)
- [ ] CLI (the command line wallet)
- [x] Deployment (the deployment process after building such as Docker, Travis, etc.)
- [ ] DEX (the Decentralized EXchange, market engine, etc.)
- [ ] P2P (the peer-to-peer network for transaction/block propagation)
- [ ] Performance (system or user efficiency, etc.)
- [ ] Protocol (the blockchain logic, consensus, validation, etc.)
- [ ] Security (the security of system or user data, etc.)
- [ ] UX (the User Experience)
- [ ] Other (please add below)

**Additional Context (optional)**
Add any other context about your request here.

## CORE TEAM TASK LIST
- [ ] Evaluate / Prioritize Feature Request
- [ ] Refine User Stories / Requirements
- [ ] Define Test Cases
- [ ] Design / Develop Solution
- [ ] Perform QA/Testing
- [ ] Update Documentation

No specific files, tests, or entry points are identified. Start by locating the Docker image build and deployment configuration, then review the linked security-update guidance and determine how periodic rebuilds should be triggered and verified. Done means the images receive updated base-image security fixes through a defined, testable process.

Written by the indexing model from the issue text.