[mqtt.awtrix3] Allow blink/fade colored text and make text effects more user friendly

[DrRSatzteil]

This PR does two things:

1. Fixes uneccessary limitations for blink and fade text settings. The Awtrix firmware allows blinking and fading for both colored and segment colored text. Only color gradients are incompatible. The binding was limiting this before this change so that text could only blink and fade as long as the defaul color (white) was used.
2. Until now, the rainbow property was overridden by every other effect: segment-colored-text, color, gradient, blink, fade. This means that you need to set all these channels to their default values or unlink the channels to be able to use the rainbow property. From an OH users perspective this is very unfortunate because activating the rainbow effect usually only requires you to activate a Switch item, but instead you would only see the effect once you changed potentially five other channel states (no easy on/off). Now the logic has been inverted so that rainbow overrides almost all other effects. This is a somewhat breaking change. Not for OH in itself but it will potentially change the way an existing app is styled on the Ulanzi clock. However this will only affect very few users if any at all and a fix would likely be relatively straight forward. Therefore I don't think this is an actual issue. The new segment-color-text feature will still override rainbow because it does not make sense to show the font-tags as text on the clock.

In addition to that this PR also fixes the README, because it was not correct about the order of overrides.

[Copilot]

Pull Request Overview

This PR relaxes text effect limitations and changes effect precedence to make rainbow easier to toggle while allowing blink/fade with colored text segments.

• Allow blink/fade to work with colored text (including segment-colored via font tags)
• Change precedence so rainbow overrides color/gradient/blink/fade (but is ignored when text has color tags)
• Update tests and README to reflect new behavior and correct channel types/usability notes

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
bundles/org.openhab.binding.mqtt.awtrixlight/src/main/java/org/openhab/binding/mqtt/awtrixlight/internal/app/AwtrixApp.java	Implements new effect precedence and allows blink/fade with color tags; adjusts color config when rainbow is enabled.
bundles/org.openhab.binding.mqtt.awtrixlight/src/test/java/org/openhab/binding/mqtt/awtrixlight/internal/HelperTest.java	Updates tests to assert rainbow overrides fade and copy semantics accordingly.
bundles/org.openhab.binding.mqtt.awtrixlight/README.md	Documents new precedence rules, fixes channel type for top-text, and updates examples.

Comments suppressed due to low confidence (1)

bundles/org.openhab.binding.mqtt.awtrixlight/README.md:1

• Fix extra space in 'is set'.

# MQTT Awtrix 3 Binding

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[lsiepel]

Thanks, LGTM