feat(rhema-code): add the colors setting with four palettes

The stored `colors` key names a palette — rhema (the default,
Jadeite), aquamarine, black-and-white, or dracula — and the
Appearance page of /settings cycles it live, like the theme and
icon toggles beside it. Each palette carries a dark and a light
appearance under the existing `theme` key; dracula's light side is
derived, the official palette ships only dark.

The appearance decision moves off token comparison: Theme now
answers is_dark() from the ground/text luminance, so palettes
beyond the original two get the right per-profile fallback tones.

android/gradle.properties

@@ -0,0 +1,5 @@
+# The system default JDK (25) is the only one with a compiler on this machine;
+# Gradle 9.3.1 runs on it. Pin nothing: `./gradlew` picks up JAVA_HOME or PATH.
+org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
+android.useAndroidX=true
+kotlin.code.style=official