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.

docker-compose.yml

@@ -19,11 +19,11 @@ services:
       # Optional webhook URL for Browserless error alerts.
       ERROR_ALERT_URL: "${ERROR_ALERT_URL:-}"
     ports:
-      - "3000:3000"
+      - "3030:3000"
     # Shared memory is required for Chrome.
     shm_size: "2gb"
     healthcheck:
-      test: ["CMD", "wget", "-qO-", "http://localhost:3000/json/version"]
+      test: ["CMD", "wget", "-qO-", "http://localhost:3030/json/version"]
       interval: 10s
       timeout: 5s
       retries: 5
@@ -54,7 +54,7 @@ services:
       kokoro:
         condition: service_healthy
     environment:
-      BROWSERLESS_URL: "http://browserless:3000"
+      BROWSERLESS_URL: "http://browserless:3030"
       BROWSERLESS_TOKEN: "${BROWSERLESS_TOKEN:-}"
       # content | scrape | cdp | direct — swap to test different strategies.
       BROWSERLESS_STRATEGY: "${BROWSERLESS_STRATEGY:-direct}"