feat: add version-aware application footer

[Willxup]

Summary

• Expose buildinfo.Version through /api/v1/status and document the required version field.
• Add a responsive application footer with repository, license, author, and runtime version details; omit the version until it is available.
• Keep the existing header structure and visual design unchanged so the approved C header remains isolated to the next pull request.

Verification

• make check
• make frontend-e2e when UI behavior changes
• Public API documentation updated when applicable
• No real configuration, credential, Cookie, database, backup, log, or private address added
• Commits include Signed-off-by (DCO)

Compatibility

The status response adds a required string version field. The bundled server and frontend are updated together; clients that validate or construct this response must include it. No configuration, database, or container changes.