Add mention of history archive path to readme

[leighmcculloch]

What

Add a mention to the README for where history archives are accessible in the quickstart image.

Why

The /archive endpoint was never documented, but it is there.

[Copilot]

Pull request overview

This PR introduces a new /history-archive endpoint with clearer semantics to expose the history archive in local mode, while maintaining the existing /archive endpoint for backwards compatibility. The change addresses the ambiguity of the term "archive" which could refer to different types of archives in the Stellar ecosystem.

• Adds new /history-archive nginx location that proxies to port 1570 (Python HTTP server serving history archive files)
• Retains /archive endpoint for backwards compatibility with existing tooling
• Documents the new endpoint in the README with appropriate local-mode-only notation

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
local/nginx/etc/conf.d/history-archive.conf	Adds new /history-archive location block with rewrite rule and proxy configuration; keeps existing /archive location with explanatory comment about backwards compatibility
README.md	Adds documentation for the new History Archive endpoint in the HTTP APIs section, noting it's only available with --local flag

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[leighmcculloch]

I've reduced this change down to documenting the current history archive URL. Now that it was pointed out over on this other issue that we shouldn't be referring to the meta as an archive, we don't really need to change this.

• Add galexie service for local ledger meta store #870 (comment)