2024-02-14 Heimdall port conflict - master branch - PR 1 of 2

[Paraphraser]

Issue #751 reports external port 8880 is used for both Heimdall and Zigbee2MQTT_Assistant. This PR changes the port to 8882:

$ git -C ~/IOTstack/.templates grep 8880
heimdall/service.yml:    - 8880:80
zigbee2mqtt_assistant/service.yml:    - "8880:80"
zigbee2mqtt_assistant/service.yml:    - VIRTUAL_PORT=8880
$ git -C ~/IOTstack/.templates grep 8882
$

Using port 8882 for HTTP also conveniently aligns with the second Heimdall port-mapping of 8883:443.

Also takes the opportunity to adopt up-to-date syntax for TZ=.

Fixes #751