Correct docker image urls

[loryanstrant]

This pull request updates the Docker image tags in both the README.md and docker-compose.yml files to use the latest and main branches instead of specific versions. This ensures that users and developers are working with the most up-to-date images and simplifies maintenance.

Docker image tag updates:

• Updated the PostgreSQL Docker image tag in the README.md example from latest-postgresql to main-postgresql to reflect the current main branch.
• Changed the LocalRecall Docker image tag in the README.md example from an untagged image to latest for clarity and consistency.
• Modified the commented-out PostgreSQL image tag in docker-compose.yml from v0.5.2-postgresql to main-postgresql to align with the main branch.
• Updated the commented-out LocalRecall image tag in docker-compose.yml from v0.5.2 to latest to use the latest available image.

[Copilot]

Pull request overview

Updates documentation and Docker Compose examples to reference branch-based / floating Docker image tags instead of specific versioned tags, aiming to keep referenced images aligned with the latest builds.

Changes:

• Update PostgreSQL image tag references to main-postgresql in README and docker-compose comments.
• Update LocalRecall image tag references to latest in README and docker-compose comments.
• Minor docker-compose volume section line adjustment (no functional change).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
docker-compose.yml	Updates commented-out image: examples for postgres and ragserver to main-postgresql / latest.
README.md	Updates manual run examples to use main-postgresql for Postgres image and :latest for LocalRecall image.

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