Add configurable deployment system with VPN and Tor support

Features:
- Hidden config.json in assets for per-deployment customization
- Configure target URL, app name, and branding
- Optional WireGuard VPN with auto-connect
- Optional Tor routing via Orbot
- Custom theme colors
- Configuration-driven app behavior

Configuration file location: app/src/main/assets/config.json
Example configuration: config.example.json

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

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

app/src/main/kotlin/uk/silverlabs/silverdroid/config/AppConfig.kt

@@ -0,0 +1,62 @@
+package uk.silverlabs.silverdroid.config
+
+import kotlinx.serialization.Serializable
+
+/**
+ * Application configuration that can be customized per deployment
+ */
+@Serializable
+data class AppConfig(
+    // App branding
+    val appName: String = "SilverDROID",
+    val appVersion: String = "1.0.0",
+
+    // Target URL configuration
+    val targetUrl: String,
+    val showUrlBar: Boolean = false,
+    val allowNavigation: Boolean = true,
+
+    // VPN configuration (optional)
+    val vpn: VpnConfig? = null,
+
+    // Tor configuration (optional)
+    val tor: TorConfig? = null,
+
+    // Theme customization
+    val theme: ThemeConfig = ThemeConfig()
+)
+
+@Serializable
+data class VpnConfig(
+    val enabled: Boolean = false,
+    val autoConnect: Boolean = true,
+    val privateKey: String,
+    val address: String,
+    val dns: List<String> = emptyList(),
+    val peers: List<PeerConfig>
+)
+
+@Serializable
+data class PeerConfig(
+    val publicKey: String,
+    val endpoint: String,
+    val allowedIps: List<String> = listOf("0.0.0.0/0"),
+    val persistentKeepalive: Int = 25
+)
+
+@Serializable
+data class TorConfig(
+    val enabled: Boolean = false,
+    val autoConnect: Boolean = true,
+    val useBridges: Boolean = false,
+    val bridges: List<String> = emptyList(),
+    val socksPort: Int = 9050,
+    val controlPort: Int = 9051
+)
+
+@Serializable
+data class ThemeConfig(
+    val primaryColor: String? = null,
+    val backgroundColor: String? = null,
+    val statusBarColor: String? = null
+)