Improve frontend test framework (#22824)

* add error allowlist file for error collector

* add error collector for console + page + request errors

* wire error collector into frigateApp fixture

* add self-tests for error collector fixture

* gate strict error mode on E2E_STRICT_ERRORS=1

* triage pre-existing errors and seed allowlist

* add mockEmpty/mockError/mockDelay helpers for state-driven tests

* add self-tests for mock override helpers

* add mobile affordance helpers to BasePage

* add lint script for banned spec patterns and @mobile rule

* apply prettier fixes to new e2e files

* rewrite export.spec.ts

* clean up

* move export spec rewrite and bugfix to separate branch