Delete dead jest harness and move specs

[Dumea Alexandru (alexdumea)]

1. Why is this change necessary?

The Administration Jest specs lived in two places that both broke Shopware's test-structure ADR (adr/2022-10-20-test-structure.md), which puts each spec next to the code it tests: src/Resources/app/administration/test/ and tests/jest/administration/. lint:admin doesn't cover administration/test/, so 14 of the 17 specs were never linted.

A second Jest setup under src/Resources/app/administration/ (jest.config.js, babel.config.js, package.json, package-lock.json) was unused as a test harness.

The release zip also shipped test scaffolding: the 14 specs in administration/test/, the dead Jest setup and the test-only PHP helpers in src/Ucp/Test. Those helpers are already kept out of production by services.php and routes.php, but they shouldn't ship at all.

2. What does this change do, exactly?

• Removes the unused Jest setup. jest.config.js, babel.config.js and package-lock.json are deleted; nothing referenced them. The live config at tests/jest/administration/jest.config.js has its own @swc/jest transform, and the admin source imports no npm packages.

• Replaces the admin package.json with a minimal one ({"private": true}), dropping the old Jest scripts and dependencies. The file has to stay: it is the nearest package.json above the admin source, and without it the plugin root's "type": "module" applies there. Webpack 5 (the 6.6 webpack build) then treats the admin .js files as strict ESM and fails on extensionless imports such as ./core-feature. A package.json without "type" keeps normal resolution, like core's admin package.json. Webpack 4 (6.5) and Vite (6.6 vite, trunk) don't apply this rule.

• Moves all 17 specs next to the code they test, under src/Resources/app/administration/src/, named the way core names them:

  • <component>.spec.js for a component's main spec;
  • <component>-<aspect>.spec.js for extra specs on the same component, like core's sw-sales-channel-detail-tabs.spec.js;
  • <file>.spec.js next to plain modules.

  Only relative paths changed. The eslint-disable comments for rules that aren't configured (import/first, global-require) were removed.

• Reduces Jest's testMatch to one glob, src/Resources/app/administration/src/**/*.spec.js. The specs now fall under the existing lint:admin scope, so eslint.config.mjs is unchanged and jest/no-disabled-tests stays at warn.

• Keeps test scaffolding out of the zip (.shopware-extension.yml):

  • src/Ucp/Test is added to pack.excludes.paths.
  • The specs are removed by a pack.before_hooks step, because excludes.paths only takes literal paths, not globs. The hook runs in the temporary build copy ($EXTENSION_DIR) before the checksums and the zip are written, so production files next to the specs still ship.

• Guards the test-only PHP helpers, so a non-prod shop installed from the zip still boots without src/Ucp/Test. Before, services.php, routes.php and TestAgentProfileFetcherCompilerPass loaded those classes whenever APP_ENV wasn't prod. They now also check class_exists() / is_dir().

• Fails the build if test scaffolding comes back. bin/ci-assert-zip-no-vendor.sh, which package-zip.yml already runs, now fails when the zip contains any *.spec.js or anything under src/Ucp/Test/. The spec removal depends on a shopware-cli hook, so this catches a future CLI change that silently stops running it.