Initial commit: Pezkuwi Wallet Android

Security hardened release:
- Code obfuscation enabled (minifyEnabled=true, shrinkResources=true)
- Sensitive files excluded (google-services.json, keystores)
- Branch.io key moved to BuildConfig placeholder
- Updated dependencies: OkHttp 4.12.0, Gson 2.10.1, BouncyCastle 1.77
- Comprehensive ProGuard rules for crypto wallet
- Navigation 2.7.7, Lifecycle 2.7.0, ConstraintLayout 2.1.4

scripts/secrets.gradle

@@ -0,0 +1,36 @@
+Properties localProperties = new Properties()
+
+def localPropertiesFile = project.rootProject.file('local.properties')
+
+if (localPropertiesFile.exists()) {
+    localProperties.load(localPropertiesFile.newDataInputStream())
+}
+
+ext.readRawSecretOrNull = { secretName ->
+    def localPropSecret = localProperties.getProperty(secretName)
+
+    def secret = (localPropSecret != null) ? localPropSecret : System.getenv(secretName)
+
+    if (secret == null || secret.isEmpty()) return null
+
+    return secret
+}
+
+ext.readStringSecretOrNull = { secretName ->
+    def secret = readRawSecretOrNull(secretName)
+    if (secret == null) return null
+
+    return maybeWrapInQuotes(secret)
+}
+
+ext.readStringSecret = { secretName ->
+    return readStringSecretOrNull(secretName) ?: secretNotFound(secretName)
+}
+
+private static def secretNotFound(secretName) {
+    throw new NoSuchElementException("${secretName} secret is not found in local.properties or environment variables")
+}
+
+static def maybeWrapInQuotes(content) {
+    return content.startsWith("\"") ? content : "\"" + content + "\""
+}