Remove dev-only DomCrawler from production /impress, /privacy, /grenzwerte path (#536)

[maltehuebner]

Summary

TemplateController::staticAction (routes /privacy, /impress, /grenzwerte) derived the page title by rendering the template a second time and parsing its <h2> with Symfony\Component\DomCrawler\Crawler + ->filter() (which additionally needs symfony/css-selector). Both symfony/dom-crawler and symfony/css-selector are require-dev-only (pulled transitively via symfony/browser-kit), so a production build with composer install --no-dev fatals with Class Symfony\Component\DomCrawler\Crawler not found on all three routes.

Changes

• Replaced the H2 parsing with an explicit title route default in config/routing/1_static.yaml (Datenschutzerklärung / Impressum / Übersicht über Schadstoffe und Grenzwerte), matching the exact previous H2 text. staticAction now takes a string $title argument bound from the route default.
• Removed readH2Tag() and with it:
  • the double full render of every static template per request,
  • the EntrypointLookup reset workaround and the now-unused EntrypointLookupCollectionInterface constructor dependency (the constructor is gone; ManagerRegistry comes from the parent),
  • the always-true ternary $h2 ? $h2->text() : null and its phpstan-baseline.neon entry.
• No production code references DomCrawler/CssSelector anymore; they remain dev-only (still used by browser-kit in the Integration test suite).

Deliberately not implemented

• Caching the remote Impress JSON (optional item): out of scope for this fix; the double-render that amplified the external call is already removed.
• A --no-dev smoke-build CI job (optional item): worth adding as a guard, but left as a follow-up to avoid coupling this focused fix to CI-pipeline changes.

Verification

• grep confirms no DomCrawler/CssSelector/Crawler/EntrypointLookupCollection references remain in src/.
• vendor/bin/phpstan analyse — No errors (baseline entry removed).
• vendor/bin/phpunit --testsuite="Project Test Suite" — 121 tests green.
• bin/console lint:container --env=prod — OK.
• bin/console debug:router privacy --env=prod — shows title: Datenschutzerklärung default.

Note: the /impress and /privacy Integration tests assert on the template's own <h2> (not the SEO title), so behaviour is unchanged; they run in the DB/network-dependent Integration suite, not exercised here.

Closes #536

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