Revert #59: restore flat Neo4j manifest (re-sequencing — land #54 first)

[colombod]

Undo the structured two-client Neo4j manifest change from #59 so PR #54 can merge cleanly.

Why

PR #54 edits amplifier-online.yaml based on the pre-#59 flat manifest form. With #59 currently merged, #54's base conflicts. This revert restores the manifest to the form #54 expects, enabling a conflict-free merge.

What's happening next

1. Land docs: remove Docker artifacts (keep S360 server image), add local-first Docker-for-Neo4j workflow #54 (v6.6.6 image, no rebase)
2. Create a fresh PR on top of docs: remove Docker artifacts (keep S360 server image), add local-first Docker-for-Neo4j workflow #54 with:
   • Structured two-client Neo4j config (from Configure structured two-client Neo4j setup in Amplifier Online manifest #59)
   • Image bump to v6.7.0
   • Updated YAML secrets

This re-sequencing preserves #54's integrity and lets the new structured work land cleanly on top.