Remove Splash Screen library and related configurations

- Delete `themes_splash.xml` and remove splash screen attributes from `themes.xml`.
- Remove `androidx.core:core-splashscreen` dependency from `build.gradle` and `libs.versions.toml`.

app/build.gradle

@@ -183,7 +183,6 @@ dependencies {
     implementation(libs.jna) {
         artifact { type = "aar" }
     }
-    implementation libs.core.splashscreen
 
     implementation libs.core.ktx
     implementation libs.activity.compose

app/src/main/res/values/themes.xml

@@ -2,8 +2,6 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
     <style name="Theme.NostrSigner" parent="Theme.AppCompat.Light.NoActionBar">
         <item name="android:statusBarColor">@color/purple_700</item>
-        <item name="windowSplashScreenBackground">@color/amber</item>
-        <item name="windowSplashScreenAnimatedIcon">@mipmap/ic_launcher</item>
         <item name="android:windowLayoutInDisplayCutoutMode" tools:ignore="NewApi">shortEdges</item>
         <item name="android:windowIsTranslucent">true</item>
     </style>

app/src/main/res/values/themes_splash.xml

@@ -1,8 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<resources xmlns:tools="http://schemas.android.com/tools">
-    <style name="Theme.SignerSplash" parent="Theme.SplashScreen">
-        <item name="windowSplashScreenBackground">@color/gray</item>
-        <item name="windowSplashScreenAnimatedIcon">@mipmap/ic_launcher_foreground</item>
-        <item name="postSplashScreenTheme">@style/Theme.NostrSigner</item>
-    </style>
-</resources>

gradle/libs.versions.toml

@@ -4,7 +4,6 @@ appcompat = "1.7.1"
 biometricKtx = "1.2.0-alpha05"
 core = "3.5.4"
 coreKtx = "1.17.0"
-coreSplashscreen = "1.2.0"
 datastorePreferences = "1.2.0"
 espressoCore = "3.7.0"
 junit = "4.13.2"
@@ -40,7 +39,6 @@ appcompat = { module = "androidx.appcompat:appcompat", version.ref = "appcompat"
 biometric-ktx = { module = "androidx.biometric:biometric-ktx", version.ref = "biometricKtx" }
 core = { module = "com.google.zxing:core", version.ref = "core" }
 core-ktx = { module = "androidx.core:core-ktx", version.ref = "coreKtx" }
-core-splashscreen = { module = "androidx.core:core-splashscreen", version.ref = "coreSplashscreen" }
 espresso-core = { module = "androidx.test.espresso:espresso-core", version.ref = "espressoCore" }
 ext-junit = { module = "androidx.test.ext:junit", version.ref = "junitVersion" }
 junit = { module = "junit:junit", version.ref = "junit" }