Set up project for .NET 8.0 compatibility

Co-authored-by: devedse <2350015+devedse@users.noreply.github.com>

Author: Copilot

DeveLanCacheUI_Backend.Tests/DeveLanCacheUI_Backend.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 

DeveLanCacheUI_Backend/DeveLanCacheUI_Backend.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <UserSecretsId>5be89f33-044f-41d5-b192-06d2df23e484</UserSecretsId>
@@ -22,13 +22,13 @@
 
   <ItemGroup>
     <PackageReference Include="DeveHashImageGenerator" Version="1.0.12" />
-    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="9.0.4" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.4" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.4">
+    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.10" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="8.0.10" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="8.0.10">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="9.0.4" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="8.0.10" />
     <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.21.2" />
     <PackageReference Include="Polly" Version="8.5.2" />
     <PackageReference Include="protobuf-net" Version="3.2.52" />