perf: optimize mobile line chart performance and remove window controls

- Remove drop-shadow filters on SVG paths on mobile (SignalChart, SummaryCurve)
- Hide scan-haze overlay (mix-blend-mode: screen) on mobile
- Remove feTurbulence noise filter on mobile (biggest perf win)
- Simplify backgrounds and box-shadows on mobile
- Remove blur transition on inactive panels
- Hide window control buttons (minimize/maximize/close) on mobile
- Configure Android release build to sign with debug keystore
- Update README with changelog and Android build instructions

src-tauri/gen/android/app/build.gradle.kts

@@ -43,6 +43,7 @@ android {
                     .plus(getDefaultProguardFile("proguard-android-optimize.txt"))
                     .toList().toTypedArray()
             )
+            signingConfig = signingConfigs.getByName("debug")
         }
     }
     kotlinOptions {
@@ -63,9 +64,10 @@ dependencies {
     implementation("androidx.activity:activity-ktx:1.10.1")
     implementation("com.google.android.material:material:1.12.0")
     implementation("androidx.lifecycle:lifecycle-process:2.10.0")
+    implementation("com.github.mik3y:usb-serial-for-android:3.9.0")
     testImplementation("junit:junit:4.13.2")
     androidTestImplementation("androidx.test.ext:junit:1.1.4")
     androidTestImplementation("androidx.test.espresso:espresso-core:3.5.0")
 }
 
-apply(from = "tauri.build.gradle.kts")
+apply(from = "tauri.build.gradle.kts")