test: expand coverage, dedupe data-driven tests, extract shared WebTestCase base (#201)

* test: expand coverage, dedupe data-driven tests, extract shared WebTestCase base

- Add #[CoversClass] to Base64Test and FilenameSanitizerTest
- Merge near-duplicate test methods into #[DataProvider] cases across
  ResetPasswordControllerTest, SettingsControllerTest, ClaimSeasonCommandTest,
  FilenameSanitizerTest, Base64Test, and SeasonRepositoryTest
- Add integration tests for previously untested controllers: public
  QuizController (quiz-taking flow), LoginController, RegistrationController,
  EliminationController, and PrepareEliminationController
- Add unit tests for Elimination and BankQuestion entity logic
- Extract shared WebTestCase setup/helpers (client, entityManager, login,
  entity lookups, CSRF token scraping) into AbstractControllerWebTestCase,
  removing duplicated boilerplate from all 14 WebTestCase files

* test: address PR review feedback

- Scope AbstractControllerWebTestCase::getCandidate/getQuizByName by
  season code (both Candidate and Quiz are only unique per season, not
  system-wide) and add a CandidateRepository regression test guarding
  against same-named candidates in different seasons
- Add missing entityManager->clear() before verifying DB state after a
  POST in PrepareEliminationControllerTest and QuestionBankControllerTest
- Add non-owner denial tests for BackofficeController::exportQuiz and
  QuizQuestionController::edit/reorder, which had IsGranted checks with
  no test coverage

* ci: publish PHPUnit coverage to GitHub code coverage

- Generate a Cobertura report alongside the existing JUnit report and
  upload it with actions/upload-code-coverage so coverage shows up on
  PRs and the default branch via GitHub's code coverage feature
- Add a step to copy both reports out of the php container before
  publishing them, since var/ is a Docker volume (see the Dockerfile's
  VOLUME /app/var/) and isn't bind-mounted to the runner — this also
  fixes the existing JUnit report publishing step, which was silently
  looking at a path that never had contets on the runner

* ci: fix coverage report paths and tolerate Code Quality not yet enabled

- Write PHPUnit's JUnit and Cobertura reports to reports/ instead of
  var/, since var/ is a Docker volume (Dockerfile's VOLUME /app/var/)
  that isn't bind-mounted to the runner - reports written there never
  reached the host, which is also why the prior junit.xml publish step
  had nothing to read. reports/ is a plain path under the project's
  bind mount, so no extra copy-out step is needed
- Set fail-on-error: false on the coverage upload step: it 404s until
  "Code Quality" is turned on for the repo under Settings > Code
  security > Code quality, a one-time manual step

tests/Repository/CandidateRepositoryTest.php

@@ -53,4 +53,22 @@ final class CandidateRepositoryTest extends DatabaseTestCase
         );
         $this->assertNotInstanceOf(Candidate::class, $result);
     }
+
+    /** Candidate names are only unique per season, so a same-named candidate in another season must not leak in. */
+    public function testGetCandidateByHashScopesByCandidateSeasonNotJustName(): void
+    {
+        $krtekSeason = $this->getSeasonByCode('krtek');
+        $anotherSeason = $this->getSeasonByCode('bbbbb');
+
+        $duplicateNamedCandidate = new Candidate('Claudia');
+        $anotherSeason->addCandidate($duplicateNamedCandidate);
+        $this->entityManager->persist($duplicateNamedCandidate);
+        $this->entityManager->flush();
+
+        $candidate = $this->candidateRepository->getCandidateByHash($krtekSeason, 'Q2xhdWRpYQ');
+
+        $this->assertInstanceOf(Candidate::class, $candidate);
+        $this->assertSame($krtekSeason, $candidate->season);
+        $this->assertNotSame($duplicateNamedCandidate, $candidate);
+    }
 }