fix: Make release signing configuration non-blocking for CI

- Remove exception throwing during configuration phase
- Set empty defaults for signing credentials to allow gradle configuration
- This fixes CI failures for dependabot PRs that don't have access to secrets
- Release builds will still fail naturally if credentials are missing

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: graycreate

app/build.gradle

@@ -24,15 +24,10 @@ android {
         release {
             // Release signing requires environment variables to be set
             // The keystore will be decoded from KEYSTORE_BASE64 in CI/CD
-            if (System.getenv("KEYSTORE_PASSWORD") != null && System.getenv("KEY_PASSWORD") != null) {
-                storeFile file("keystore.jks")
-                storePassword System.getenv("KEYSTORE_PASSWORD")
-                keyAlias System.getenv("KEY_ALIAS")?.trim() ?: "ghui"
-                keyPassword System.getenv("KEY_PASSWORD")
-            } else {
-                // Release builds require proper environment variables
-                throw new GradleException("Release builds require signing configuration. Please set KEYSTORE_PASSWORD and KEY_PASSWORD environment variables.")
-            }
+            storeFile file("keystore.jks")
+            storePassword System.getenv("KEYSTORE_PASSWORD") ?: ""
+            keyAlias System.getenv("KEY_ALIAS")?.trim() ?: "ghui"
+            keyPassword System.getenv("KEY_PASSWORD") ?: ""
         }
     }