Production cleanup: enable R8, add ProGuard rules, validate API input

- Enable R8 minification and resource shrinking for release builds
- Add ProGuard keep rules for Ktor, kotlinx.serialization, Room
- Validate hour/minute range in POST /set endpoint
- Guard wake lock release on server start failure
- Remove unused template colors from colors.xml
- Rewrite README with curl examples, security note, troubleshooting

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/build.gradle.kts

@@ -34,7 +34,8 @@ android {
     }
     buildTypes {
         release {
-            isMinifyEnabled = false
+            isMinifyEnabled = true
+            isShrinkResources = true
             proguardFiles(
                 getDefaultProguardFile("proguard-android-optimize.txt"),
                 "proguard-rules.pro"

app/proguard-rules.pro

@@ -1,21 +1,27 @@
-# Add project specific ProGuard rules here.
-# You can control the set of applied configuration files using the
-# proguardFiles setting in build.gradle.
-#
-# For more details, see
-#   http://developer.android.com/guide/developing/tools/proguard.html
+# Ktor — keep CIO engine and routing
+-keep class io.ktor.** { *; }
+-keepclassmembers class io.ktor.** { *; }
+-dontwarn io.ktor.**
 
-# If your project uses WebView with JS, uncomment the following
-# and specify the fully qualified class name to the JavaScript interface
-# class:
-#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
-#   public *;
-#}
+# kotlinx.serialization — keep @Serializable classes
+-keepattributes *Annotation*, InnerClasses
+-dontnote kotlinx.serialization.AnnotationsKt
+-keepclassmembers @kotlinx.serialization.Serializable class ** {
+    *** Companion;
+}
+-keepclasseswithmembers class ** {
+    kotlinx.serialization.KSerializer serializer(...);
+}
+-keep,includedescriptorclasses class com.example.helios_alarm_clock.**$$serializer { *; }
+-keepclassmembers class com.example.helios_alarm_clock.** {
+    *** Companion;
+}
+-keepclasseswithmembers class com.example.helios_alarm_clock.** {
+    kotlinx.serialization.KSerializer serializer(...);
+}
 
-# Uncomment this to preserve the line number information for
-# debugging stack traces.
-#-keepattributes SourceFile,LineNumberTable
+# Room — keep entities
+-keep class com.example.helios_alarm_clock.data.AlarmEntity { *; }
 
-# If you keep the line number information, uncomment this to
-# hide the original source file name.
-#-renamesourcefileattribute SourceFile
+# SLF4J (Ktor dependency) — suppress missing impl warnings
+-dontwarn org.slf4j.**

app/src/main/java/com/example/helios_alarm_clock/service/KtorService.kt

@@ -54,7 +54,13 @@ class KtorService : Service() {
         super.onCreate()
         acquireWakeLock()
         startForeground(NOTIFICATION_ID, buildNotification())
-        startServer()
+        try {
+            startServer()
+        } catch (e: Exception) {
+            releaseWakeLock()
+            stopSelf()
+            return
+        }
         rescheduleAlarms()
     }
 
@@ -111,6 +117,13 @@ class KtorService : Service() {
                 post("/set") {
                     try {
                         val req = call.receive<SetAlarmRequest>()
+                        if (req.hour !in 0..23 || req.minute !in 0..59) {
+                            call.respond(
+                                HttpStatusCode.BadRequest,
+                                ErrorResponse("hour must be 0-23, minute must be 0-59")
+                            )
+                            return@post
+                        }
                         val id = UUID.randomUUID().toString()
 
                         val now = Calendar.getInstance()

app/src/main/res/values/colors.xml

@@ -1,10 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <color name="purple_200">#FFBB86FC</color>
-    <color name="purple_500">#FF6200EE</color>
-    <color name="purple_700">#FF3700B3</color>
-    <color name="teal_200">#FF03DAC5</color>
-    <color name="teal_700">#FF018786</color>
     <color name="black">#FF000000</color>
     <color name="white">#FFFFFFFF</color>
-</resources>
+</resources>