refactor(ios): host the upload route and the REST relay on an editor local server

[dcalhoun]

What?

Replaces MediaUploadServer with an EditorLocalServer that takes registered routes. The upload handler becomes a MediaUploadRoute, and RestRelay conforms to the same LocalServerRoute protocol instead of occupying an optional slot on the upload server.

Stacked on #611. A mechanical refactor with no behavior change: the JS contract (nativeUploadPort, nativeUploadToken, networkProxy), the relay's /proxy route, the server name and limits, and every test assertion are unchanged.

Why?

#611 bolted the REST relay onto a media-specific server: an optional restRelay constructor parameter, a path-prefix check ahead of the upload route, two booleans on the view controller mirroring what it passed in, and ternaries in buildEditorConfiguration reading them. Each further route (asset cache, oEmbed proxy, the any-origin transport) would add one of each. Once the relay accepts any origin it is the editor's general transport and the upload route is one client of it, so a media server hosting the transport is inverted. Raised by the /code-review run on #611.

How?

• LocalServerRoute: handles(_:) and handle(_:). The relay conforms with a one-line forward to its existing static predicate.
• MediaUploadRoute: the upload handler and everything it calls, owning the delegate (weakly, as before) and the default uploader, plus the orphan sweep and its awaitable cleanupTask.
• EditorLocalServer.start(routes:maxRequestBodySize:): owns the listener configuration that was already relay-aware, hands each request to the first route that claims it, and answers hosts(_:). The media-upload name is kept so an upgrade does not strand the temp directory.
• EditorViewController builds the route list from the same two conditions it already evaluated and advertises to JavaScript only what the server hosts. The two booleans and their reset on a failed start are gone.
• Files move under Sources/LocalServer/ and Tests/LocalServer/; the combined server test file splits by type.

Each commit leaves the suite green. Deferred: the server's 404 and parse-error refusals still carry the code upload_error, and the 413 message is upload-worded. Changing those is behavior, so it belongs with the any-origin work.

Testing Instructions

1. make test-swift-library — 1013 tests, 61 suites.
2. In the demo app, with an upload delegate set, upload an image: it goes through the native route as before.
3. With Lockdown Mode on (or the debug override), load a post and save it: REST traffic is relayed as on fix(ios): route editor REST requests through a native relay under Lockdown Mode #611.

Accessibility Testing Instructions

No UI change.

Screenshots or screencast

None.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PfwJZw19TxukV3iLkbVECB

[wpmobilebot]

XCFramework Build

This PR's XCFramework is available for testing. Add the following to your Package.swift:

.package(url: "https://github.com/wordpress-mobile/GutenbergKit", branch: "pr-build/619")

_{Built from 963882b}