chore: update Browserless port references from 3000 to 3030

Update all default URLs, port mappings, healthcheck endpoints, Dockerfile
ENV defaults, and integration test run instructions to use port 3030.

scraper/internal/browser/integration_test.go

@@ -7,7 +7,7 @@
 //
 // Run them with:
 //
-//	BROWSERLESS_URL=http://localhost:3000 \
+//	BROWSERLESS_URL=http://localhost:3030 \
 //	BROWSERLESS_TOKEN=your-token \          # omit if auth is disabled
 //	go test -v -tags integration -timeout 120s \
 //	    github.com/libnovel/scraper/internal/browser