v0.5.2 — commit fixed debug keystore for stable signing

Every CI build previously minted a fresh debug keystore, so each release failed
to install over the last (signature mismatch) — forcing an uninstall and loss of
the on-device proxy token. Commit a fixed debug.keystore (a debug key is
non-secret; password is the well-known "android") and point the debug
signingConfig at it, so CI and local builds sign identically and updates install
in place. No functional app changes.

versionCode 17 -> 18, versionName 0.5.1 -> 0.5.2.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015jgJnzMr2bdNuWcDX2xRUR

app/build.gradle.kts

@@ -12,8 +12,21 @@ android {
         applicationId = "org.soulstone.overwatch"
         minSdk = 26
         targetSdk = 35
-        versionCode = 17
-        versionName = "0.5.1"
+        versionCode = 18
+        versionName = "0.5.2"
+    }
+
+    // Fixed debug keystore committed to the repo (a debug key is non-secret — its
+    // password is the well-known "android") so CI and local builds sign
+    // identically. Without it each CI build minted a fresh debug key and updates
+    // wouldn't install over the previous one.
+    signingConfigs {
+        getByName("debug") {
+            storeFile = rootProject.file("debug.keystore")
+            storePassword = "android"
+            keyAlias = "androiddebugkey"
+            keyPassword = "android"
+        }
     }
 
     buildTypes {