fix: use container-internal port 3000 for browserless inter-container and healthcheck URLs

The 3030:3000 port mapping only exposes port 3030 on the host. Container-to-container
traffic (scraper → browserless) and the healthcheck (which runs inside the browserless
container) must use the container's own port 3000. Only the host-side default in
main.go and the Dockerfile ENV remain on 3030.

docker-compose.yml

@@ -23,7 +23,7 @@ services:
     # Shared memory is required for Chrome.
     shm_size: "2gb"
     healthcheck:
-      test: ["CMD", "wget", "-qO-", "http://localhost:3030/json/version"]
+      test: ["CMD", "wget", "-qO-", "http://localhost:3000/json/version"]
       interval: 10s
       timeout: 5s
       retries: 5
@@ -54,7 +54,7 @@ services:
       kokoro:
         condition: service_healthy
     environment:
-      BROWSERLESS_URL: "http://browserless:3030"
+      BROWSERLESS_URL: "http://browserless:3000"
       BROWSERLESS_TOKEN: "${BROWSERLESS_TOKEN:-}"
       # content | scrape | cdp | direct — swap to test different strategies.
       BROWSERLESS_STRATEGY: "${BROWSERLESS_STRATEGY:-direct}"