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/build.gradle.kts

@@ -0,0 +1,6 @@
+plugins {
+    id("com.android.application") version "8.13.2" apply false
+    id("org.jetbrains.kotlin.android") version "2.2.21" apply false
+    id("org.jetbrains.kotlin.plugin.compose") version "2.2.21" apply false
+    id("org.jetbrains.kotlin.plugin.serialization") version "2.2.21" apply false
+}