Update ESPHome to 2026.3.1

Author: github-actions[bot]

.github/workflows/publish-firmware.yml

@@ -18,7 +18,7 @@ jobs:
         project-template-esp32-c3.factory.yaml
         project-template-esp32-c6.factory.yaml
         project-template-esp32-s3.factory.yaml
-      esphome-version: 2026.2.4
+      esphome-version: 2026.3.1
       combined-name: project-template
       #### Modify above here to match your project ####