fix(ci): use valid 32-byte base64 encryption key for E2E tests

The DNS provider API endpoints were returning 404 in CI because the
encryption service failed to initialize with an invalid key.

Changed CHARON_ENCRYPTION_KEY from plain text to valid base64 string
Key "dGVzdC1lbmNyeXB0aW9uLWtleS1mb3ItY2ktMzJieXQ=" decodes to 32 bytes
Without valid encryption key, DNS provider routes don't register
This was causing all dns-provider-types.spec.ts tests to fail
Root cause: AES-256-GCM requires exactly 32 bytes for the key

.github/workflows/docker-build.yml

@@ -853,7 +853,7 @@ jobs:
             -p 8080:8080 \
             -e CHARON_ENV=development \
             -e CHARON_DEBUG=1 \
-            -e CHARON_ENCRYPTION_KEY=test-key-for-ci-only-not-production \
+            -e CHARON_ENCRYPTION_KEY=dGVzdC1lbmNyeXB0aW9uLWtleS1mb3ItY2ktMzJieXQ= \
             "${IMAGE_REF}"
 
       - name: Wait for application health