Depend on slint directly in the Android app

android_main takes an AndroidApp and calls slint::android::init, both of
which come from slint itself rather than from dr-ui. The backend feature
still arrives through dr-ui's target-specific dependency. anyhow was unused.

Assisted-by: LLM

Cargo.lock

@@ -1158,9 +1158,9 @@ name = "darkroom-android"
 version = "0.1.0"
 dependencies = [
  "android_logger",
- "anyhow",
  "dr-ui",
  "log",
+ "slint",
 ]
 
 [[package]]

apps/darkroom-android/Cargo.toml

@@ -16,7 +16,10 @@ crate-type = ["cdylib"]
 # No backend feature to select: dr-ui picks its Slint backend from the target,
 # so building for aarch64-linux-android gets android-activity automatically.
 dr-ui.workspace = true
-anyhow.workspace = true
+# Directly, not just through dr-ui: `android_main` takes an `AndroidApp` and
+# calls `slint::android::init`, both of which come from this crate. The backend
+# feature comes from dr-ui's target-specific dependency.
+slint.workspace = true
 log.workspace = true
 android_logger = "0.15"