deps: bump @angular/platform-server to 21.2.22

[katsugtgz]

Updates @angular/platform-server from 21.2.8 to 21.2.22.

Evidence:

• package.json pinned @angular/platform-server@21.2.8
• osv-scanner reported GHSA-v3p8-whq6-r5jg, GHSA-f6mr-pjwc-34m4, GHSA-45q2-gjvg-7973, GHSA-gxx4-3xcv-f8qx, GHSA-hqr9-c56f-3x7f, GHSA-rfh7-fxqc-q52v, GHSA-vpx6-8pjr-4g3v, GHSA-xrxm-cp7j-8xf6 for that version
• updated version: 21.2.22

Validation:

• osv-scanner no longer reports those advisories for @angular/platform-server after the update
• npx ng build passes (prerendered 6 routes, only a pre-existing bundle budget warning)
• npx ng test --no-watch passes (14 files, 56 tests)

Scope: dependency update only (package.json, package-lock.json).