Change splash screen and Remove "loading..." text during startup

### Splash Screen
When starting the app a purple color is shown with .NET written in the middle.

#### Suggestion
- Inside subtrack.maui.csproj the splash screen is defined and you can change the background color there.
- The above works but still displays ".NET". We can add our own svg ~~by creating an SVG using an online editor such as https://editor.method.ac/ and~~ then naming it _splash.svg_ and adding it to the folder inside **subtrack.MAUI\Resources\Splash**. ~~and have the text "subtrack" in either a white color or light blue like the one used around our cards (might be this hex **#2a9fd6**)~~
- The theme should be dark, use a black **#000000** background ~~or the grey one that is used for our subscription cards (might be this **#222**)~~
- ~~An icon next to the text would be nice but is not a requirement~~
- The icon here should be the same as the one used for #109

#### **Update**
Use the same icon and colors as the app icon added in #165

### Loading Text
The "loading" text after the splash screen is just an unnecessary flash as it is barely shown for one second.

#### Suggestion
- Inside index.html simply only remove the "loading..." text.