Use .buildcount file for unique auto-incrementing versionCode

Build counter is incremented by deploy.ps1 on every deploy, ensuring
unique versionCode even from the same commit. File is gitignored.

app/build.gradle.kts

@@ -14,18 +14,19 @@ fun gitVersionName(): String = runGit("describe", "--tags", "--abbrev=0")
     .removePrefix("v")
     .ifEmpty { "0.1.0" }
 
-// Build number = total commits (always increments) + offset for store history
-const val VERSION_CODE_OFFSET = 4
-fun gitBuildNumber(): Int = (runGit("rev-list", "--count", "HEAD")
-    .toIntOrNull() ?: 1) + VERSION_CODE_OFFSET
+// Build number from .buildcount file (incremented by deploy.ps1)
+fun buildNumber(): Int {
+    val file = rootProject.file(".buildcount")
+    return if (file.exists()) file.readText().trim().toIntOrNull() ?: 1 else 1
+}
 
 fun gitShortHash(): String = runGit("rev-parse", "--short", "HEAD")
     .ifEmpty { "unknown" }
 
-// Display: "0.1.0+5.abc1234"
+// Display: "0.1.0+6.abc1234"
 fun gitDisplayVersion(): String {
     val base = gitVersionName()
-    val build = gitBuildNumber()
+    val build = buildNumber()
     val hash = gitShortHash()
     return "$base+$build.$hash"
 }
@@ -63,7 +64,7 @@ android {
         applicationId = "com.omixlab.lckcontrol"
         minSdk = 32
         targetSdk = 34
-        versionCode = gitBuildNumber()
+        versionCode = buildNumber()
         versionName = gitVersionName()
 
         buildConfigField("String", "DISPLAY_VERSION", "\"${gitDisplayVersion()}\"")