Release signing from env, version 0.1.0, minSdk 26

Signed with the local release keystore when CASTARR_STORE_* env vars are
set; minSdk raised to 26 to match the adaptive-icon-only resources.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/build.gradle.kts

@@ -9,16 +9,33 @@ android {
 
     defaultConfig {
         applicationId = "dev.castarr.tv"
-        minSdk = 23
+        minSdk = 26
         targetSdk = 35
         versionCode = 1
-        versionName = "1.0.0"
+        versionName = "0.1.0"
+    }
+
+    // Release signing from environment (see ~/.keys/castarr-release.env on the
+    // build host); unsigned release build when unset.
+    val storeFileEnv = System.getenv("CASTARR_STORE_FILE")
+    if (storeFileEnv != null) {
+        signingConfigs {
+            create("release") {
+                storeFile = file(storeFileEnv)
+                storePassword = System.getenv("CASTARR_STORE_PASSWORD")
+                keyAlias = System.getenv("CASTARR_KEY_ALIAS")
+                keyPassword = System.getenv("CASTARR_STORE_PASSWORD")
+            }
+        }
     }
 
     buildTypes {
         release {
             isMinifyEnabled = true
             proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+            if (storeFileEnv != null) {
+                signingConfig = signingConfigs.getByName("release")
+            }
         }
     }