Update containers.md to fix podman image qualification

[alex-mazzariol]

Description

This PR fixes no numbered issue, but just a minor documentation inconsistency with the usage of podman to run localAI.

[localai-org-maint-bot]

@mudler Good to merge. The Podman commands now use fully qualified Docker Hub image names, which avoids short-name resolution failures and prompts. I tightened the explanatory paragraph on the contributor branch so it does not claim that every Podman installation requires qualification. The contributor commit passes DCO, and the final diff passes git diff --check.

[localai-org-maint-bot]

Review pass. The change is correct and complete. One blocker.

Podman's unqualified-search-registries genuinely makes short names ambiguous or interactive, and every podman run example is now fully qualified. I checked the head revision: the two remaining unprefixed podman run lines (containers.md:232 and :258) are multi-line commands whose image argument was updated correctly. The explanatory paragraph up front is the right place for the rationale.

Blocking: DCO. Commit 54928279 ("docs(containers): clarify Podman image names") has no Signed-off-by. gh pr checks reports DCO fail. Re-signing the commit is all this needs.

Minor, and defensible: the reference tables now show docker.io/localai/localai:... under a column headed "Docker Hub", which is slightly redundant for Docker users. Reasonable since the tables serve both engines, but it is beyond "fix podman image qualification".