[codex] Refresh deployment and architecture docs

[macterra]

What changed

Refreshes the top-level docs that had drifted from the current repo layout and running stack.

Updated:

• README.md
• docs/deployment.md
• docs/lightning-zap-sequence.md
• docs/nginx-proxy.conf.example

Highlights:

• fixes stale app and file-path references in the main README
• updates local UI URLs and current npm pin
• aligns the deployment guide with current compose services, ports, Herald/Drawbridge/Lightning mediator layout, bundled LNbits image, and satoshi wallet location
• updates the Lightning zap flow docs to reflect mediator-owned Lightning operations instead of Drawbridge talking to LNbits directly
• clarifies that internal service-to-service admin auth uses X-Archon-Admin-Key

Why

These docs were describing older app names, older file paths, and an outdated Lightning architecture. The code and compose files had moved forward, but the operator-facing docs had not kept up.

Impact

• makes the quick-start and deployment docs match the current repo
• reduces confusion around the current wallet UIs and service ports
• keeps the Lightning flow docs consistent with the mediator-first implementation
• makes the reverse-proxy example clearer about public auth vs internal admin auth

Validation

• verified referenced ports, service names, and endpoints against the current docker-compose*.yml files and repo layout
• verified Gatekeeper and Drawbridge verification endpoints against current server routes

Notes

This is a docs-only PR. No runtime code changed.