fix: keep the Playwright config out of the Docker build context

The e2e directory is excluded from the image, but its config file was
not, and Next type-checks it during the build — so adding the end-to-end
suite broke `docker build` with a missing-module error two stages deep.

Caught by running the whole verification rather than the part that had
just changed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012cSY9pVhZmJUKNN7wf1Myd

.dockerignore

@@ -8,7 +8,12 @@ node_modules
 !.env.example
 coverage
 .preview
+# The e2e directory is excluded, so its config must be too: Next type-checks
+# playwright.config.ts during the build and it imports from ./e2e.
 e2e
+playwright.config.ts
+playwright-report
+test-results
 tests
 backups
 *.md