Set TESTS_MQTT_BROKER_HOST globally for all jobs with mosquitto services (#989)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: thomasnordquist <7721625+thomasnordquist@users.noreply.github.com>

.github/workflows/docker-browser.yml

@@ -30,6 +30,10 @@ jobs:
       packages: write
       id-token: write
 
+    env:
+      TESTS_MQTT_BROKER_HOST: localhost
+      TESTS_MQTT_BROKER_PORT: 1883
+
     services:
       # MQTT broker for testing
       mosquitto:
@@ -191,8 +195,6 @@ jobs:
           MQTT_EXPLORER_USERNAME: test
           MQTT_EXPLORER_PASSWORD: test123
           BROWSER_MODE_URL: http://localhost:3000
-          MQTT_BROKER_HOST: localhost
-          MQTT_BROKER_PORT: 1883
 
       - name: Clean up browser test container
         if: always()