v7.5: wallet linking for MAP token rewards

- Add walletAddress field to SettingsDataStore
- Settings screen: input field, QR scanner, address validation
- Include wallet_address in detection uploads to API
- Show linked wallet status in main UI (green wallet icon)
- Cardano address validation (addr1/stake1 prefixes)
- Version bumped to 1.7.5 (versionCode 11)
- APK built and signed at varroa-v7.5.apk

app/build.gradle.kts

@@ -13,8 +13,8 @@ android {
         applicationId = "com.adamaps.varroa"
         minSdk = 26
         targetSdk = 34
-        versionCode = 10
-        versionName = "1.7.4"
+        versionCode = 11
+        versionName = "1.7.5"
 
         vectorDrawables {
             useSupportLibrary = true
@@ -78,5 +78,11 @@ dependencies {
     implementation(libs.work.runtime.ktx)
     // SSH connectivity for device_id fallback
     implementation("com.jcraft:jsch:0.1.55")
+    // QR Code scanning
+    implementation("com.google.zxing:core:3.5.2")
+    implementation("com.journeyapps:zxing-android-embedded:4.3.0")
+    implementation("androidx.camera:camera-camera2:1.3.0")
+    implementation("androidx.camera:camera-lifecycle:1.3.0")
+    implementation("androidx.camera:camera-view:1.3.0")
     debugImplementation(libs.androidx.ui.tooling)
 }