♻️(frontend) switch to Authorization Code flow

Instead of interacting with Keycloak, the frontend navigate to the
/authenticate endpoint, which starts the Authorization code flow.

When the flow is done, the backend redirect back to the SPA,
passing a session cookie and a csrf cookie.

Done:
- Query GET user/me to determine if user is authenticated yet
- Remove Keycloak js dependency, as all the OIDC logic is handled by the backend
- Store user's data instead of the JWT token

src/frontend/apps/desk/package.json

@@ -39,7 +39,6 @@
     "fetch-mock": "9.11.0",
     "jest": "29.7.0",
     "jest-environment-jsdom": "29.7.0",
-    "keycloak-js": "23.0.6",
     "node-fetch": "2.7.0",
     "prettier": "3.2.5",
     "stylelint": "16.2.1",