Refactor solution structure and update dependencies

Replaced `Codebreaker.Backend.sln` with `Codebreaker.Backend.slnx`, reorganizing projects into structured folders for improved clarity and maintainability.

Updated `Directory.Packages.props` to disable transitive pinning and upgraded multiple package dependencies to their latest versions, including Aspire, Azure, Microsoft, OpenTelemetry, and NUnit packages. Removed older package versions and added updated counterparts to enhance compatibility and performance.

Author: christiannagel

src/Codebreaker.Backend.sln

@@ -0,0 +1,40 @@
+<Solution>
+  <Folder Name="/bot/">
+    <Project Path="services/bot/CodeBreaker.Bot.Tests/CodeBreaker.Bot.Tests.csproj" />
+    <Project Path="services/bot/CodeBreaker.Bot/CodeBreaker.Bot.csproj" />
+    <Project Path="services/bot/Codebreaker.BotQ/Codebreaker.BotQ.csproj" />
+  </Folder>
+  <Folder Name="/clients/">
+    <Project Path="services/Codebreaker.Blazor/src/CodeBreaker.Blazor.Client/CodeBreaker.Blazor.Client.csproj" />
+    <Project Path="services/Codebreaker.Blazor/src/CodeBreaker.Blazor.UI/CodeBreaker.Blazor.UI.csproj" />
+    <Project Path="services/Codebreaker.Blazor/src/CodeBreaker.Blazor/CodeBreaker.Blazor.csproj" />
+  </Folder>
+  <Folder Name="/common/">
+    <Project Path="services/common/Codebreaker.ServiceDefaults/Codebreaker.ServiceDefaults.csproj" />
+  </Folder>
+  <Folder Name="/gameapis/">
+    <Project Path="services/gameapis/Codebreaker.CosmosCreate/Codebreaker.CosmosCreate.csproj" />
+    <Project Path="services/gameapis/Codebreaker.GameAPIs.Playwright/Codebreaker.GameAPIs.Playwright.csproj" />
+    <Project Path="services/gameapis/Codebreaker.GameAPIs.Tests/Codebreaker.GameAPIs.Tests.csproj" />
+    <Project Path="services/gameapis/Codebreaker.GameAPIs/Codebreaker.GameAPIs.csproj" />
+    <Project Path="services/gameapis/Codebreaker.IntegrationTests/Codebreaker.IntegrationTests.csproj" />
+    <Project Path="services/gameapis/Codebreaker.SqlServerMigration/Codebreaker.SqlServerMigration.csproj" />
+  </Folder>
+  <Folder Name="/gateway/">
+    <Project Path="services/gateway/Codebreaker.ApiGateway.Identities/Codebreaker.ApiGateway.Identities.Client/Codebreaker.ApiGateway.Identities.Client.csproj" />
+    <Project Path="services/gateway/Codebreaker.ApiGateway.Identities/Codebreaker.ApiGateway.Identities/Codebreaker.ApiGateway.Identities.csproj" />
+    <Project Path="services/gateway/Codebreaker.ApiGateway/Codebreaker.ApiGateway.csproj" />
+  </Folder>
+  <Folder Name="/host/">
+    <Project Path="services/host/Codebreaker.AppHost/Codebreaker.AppHost.csproj" />
+  </Folder>
+  <Folder Name="/live/">
+    <Project Path="services/live/Codebreaker.Live/Codebreaker.Live.csproj" />
+  </Folder>
+  <Folder Name="/ranking/">
+    <Project Path="services/ranking/Codebreaker.Ranking/Codebreaker.Ranking.csproj" />
+  </Folder>
+  <Folder Name="/users/">
+    <Project Path="services/user/CodeBreaker.UserService/CodeBreaker.UserService.csproj" />
+  </Folder>
+</Solution>