host: move to Car App Library 1.8

Apps built on 1.8 can now hand Gearslip their newer template pieces (chips,
progress bars, timers); drawing them comes next. Vela, Organic Maps and RF
Sentinel connect as before.

gradle/libs.versions.toml

@@ -8,7 +8,7 @@ espressoCore = "3.7.0"
 lifecycleRuntimeKtx = "2.10.0"
 activityCompose = "1.13.0"
 composeBom = "2026.05.01"
-carApp = "1.7.0"
+carApp = "1.8.0-rc01"
 appcompat = "1.7.1"
 material = "1.14.0"
 constraintlayout = "2.2.1"