Add healthcheck in Dockerfile

[mik-laj]

Part of: Koenkk/zigbee2mqtt#28893

This adds a basic health check.
A more complete check (including whether the HTTP server is connected to MQTT) would be useful, but that’ll require server-side changes — so it’s better left for a follow-up.
Even so, this should already improve web server stability, since the Supervisor won’t route traffic to the app until it can accept HTTP requests.

[Copilot]

Pull Request Overview

This PR adds a basic HTTP health check to the Dockerfile to improve web server stability by ensuring the container can accept HTTP requests before routing traffic to it.

• Adds validation to confirm curl is available in the final Docker image
• Implements a health check that tests HTTP connectivity on port 8099
• Configures health check with 1-minute intervals and 3-second timeout

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[Copilot]

Corrected capitalization of 'CURL' to 'curl'.

Suggested change

	# Validation to confirm that CURL is installed in the final image.
	# Validation to confirm that curl is installed in the final image.

[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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