[indexer] add FlowChain control plane API

[FlowmemoryAI]

Summary

Publishes the indexer worktree output for the FlowChain private/local L1 testnet package.

Scope

• Branch: $branch
• Worktree: $(System.Collections.Hashtable.Path)
• Target: private/local FlowChain testnet for second-computer validation
• Not production mainnet, tokenomics, audited cryptography, public validators, or production bridge deployment

Checks

git diff --check; npm test

Notes

This is intentionally opened as a draft PR for review and integration sequencing.