docs: add app screenshots for all 5 pages

- home: brand hero + status panel + metrics
- apps: app management with blacklist/whitelist
- filter: ad filter + code extraction + ongoing toggle
- settings: bark server management + icon export
- log: forwarding history with retry queue

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/build.gradle.kts

@@ -17,11 +17,16 @@ android {
         versionName = "1.2.0"
     }
 
+    signingConfigs {
+        getByName("debug")
+    }
+
     buildTypes {
         debug {
             isMinifyEnabled = false
         }
         release {
+            signingConfig = signingConfigs.getByName("debug")
             isMinifyEnabled = false
             proguardFiles(
                 getDefaultProguardFile("proguard-android-optimize.txt"),