docs: update to Angular 19

[alex-okrushko]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

Most of it was automated migration

• Update to latest Angular 19
• Update angular/fire to 19 as well (they are now version-matching)
• disable Polaris as it's causing issues (trying to get the non-existent dependency)

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Closes #

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[netlify]

❌ Deploy Preview for ngrx-io failed.

Name	Link
🔨 Latest commit	fc46c4a
🔍 Latest deploy log	https://app.netlify.com/sites/ngrx-io/deploys/6806b2e23534c80008ac56dd

[timdeschryver]

@alex-okrushko Since we recently have a PR open to update the docs site (#4764) I wonder if we can close this PR. What's your opinion on this, do you think it's still useful?