Finish axios migration via shared native HTTP helper

Replace all in-scope axios callsites with a new helpers/http.js wrapper over native fetch, including JSON/text GET, JSON POST, HEAD checks, and transient 5xx retry behavior; update all browser, build, script, and proxy API clients to use it; add focused unit tests; and remove axios from package dependencies.

Constraint: Preserve API/build and deployment behavior while lowering transport surface area.

Rejected: inline fetch replacements at each callsite | rejected to avoid inconsistent error/retry semantics.

Confidence: high

Scope-risk: moderate

Directive: Keep helper in place as the transport boundary and update tests when changing request semantics.

Tested: pnpm run -s typecheck, pnpm -s run test-prebuild, pnpm -s run test, pnpm -s run test:browser, pnpm -s run netlify-build, smoke GETs on /apple-silicon-app-test and /apple-silicon-app-test/?version=2

Not-tested: branch/netlify deployment health in CI pipeline after merge

helpers/app-files-scanner.js

@@ -1,9 +1,9 @@
 import plist from 'plist'
-import axios from 'axios'
 import prettyBytes from 'pretty-bytes'
 import * as zip from '@zip.js/zip.js'
 
 import { isString } from './check-types.js'
+import { postJson } from './http.js'
 import parseMacho from './macho/index.js'
 
 // Vite Web Workers - https://vitejs.dev/guide/features.html#web-workers
@@ -331,14 +331,13 @@ export default class AppFilesScanner {
 
         // console.log( 'this.testResultStore', this.testResultStore )
 
-        const { supportedVersionNumber } = await axios.post( this.testResultStore , {
+        const responseData = await postJson( this.testResultStore, {
             filename,
             appVersion,
             result,
             machoMeta: JSON.stringify( machoMeta ),
             infoPlist: JSON.stringify( infoPlist )
-        })
-            .then( response => response.data )
+        } )
             .catch(function (error) {
                 console.error(error)
 
@@ -348,7 +347,7 @@ export default class AppFilesScanner {
             })
 
         return {
-            supportedVersionNumber
+            supportedVersionNumber: responseData?.supportedVersionNumber ?? null
         }
     }