Migrate frontend to yarn 4 (#71)

### Description
Since we are no longer tracking `frontend/.yarn/`, and
[yarnrc.yml](https://github.com/Kryha/KREAd/blob/develop/frontend/.yarnrc.yml)
points to it, yarn breaks.

Coincidentally, [yarn 4](https://yarnpkg.com/blog/release/4.0) just
landed and it seems to solve the issue with Corepack:
> "...we used to recommend using the
[yarnPath](https://yarnpkg.com/configuration/yarnrc#yarnPath) setting
pointing to a checked-in binary, but this pattern increased friction
more than we liked - many people didn't like the idea of adding a binary
to their repository, however small. We listened, and worked conjointely
with Node.js on a project called
[Corepack](https://nodejs.org/api/corepack.html). Corepack is a tool
shipped with Node.js 16+ that will automatically select the right
package manager version to run depending on the project you're working
on"

### Acceptance Criteria
- [x] yarn does not depend on `/frontend/.yarn` 
- [x] QAd

frontend/.yarnrc.yml

@@ -1,12 +1,15 @@
-nodeLinker: node-modules
+compressionLevel: mixed
+
+enableGlobalCache: false
+
 nmHoistingLimits: workspaces
 
+nodeLinker: node-modules
+
+# TODO: remove azure dependency
 npmScopes:
   kryha:
     npmRegistryServer: "https://pkgs.dev.azure.com/Kryha-io/_packaging/Kryha-io/npm/registry"
 
-plugins:
-  - path: .yarn/plugins/@yarnpkg/plugin-workspace-tools.js
-    spec: "@yarnpkg/plugin-workspace-tools"
-
-yarnPath: .yarn/releases/yarn-3.1.1.cjs
+# using package.json's packageManager instead of yarnPath
+# yarnPath: .yarn/releases/yarn-4.0.0.cjs

frontend/package.json

@@ -98,5 +98,6 @@
     "vite": "^3.0.7",
     "vite-plugin-svgr": "^2.2.1",
     "vite-tsconfig-paths": "^3.5.0"
-  }
+  },
+  "packageManager": "[email protected]"
 }