refactor: rename namespace to FiscalFlow and upgrade to .NET 10

- Rename InvoiceMaster.* to FiscalFlow.* namespace
- Upgrade from .NET 8 to .NET 10
- Update all NuGet packages to latest versions
- Update C# language version to 14.0

backend/tests/FiscalFlow.UnitTests/obj/Debug/net8.0/.NETCoreApp,Version=v8.0.AssemblyAttributes.cs

@@ -0,0 +1,4 @@
+// <autogenerated />
+using System;
+using System.Reflection;
+[assembly: global::System.Runtime.Versioning.TargetFrameworkAttribute(".NETCoreApp,Version=v8.0", FrameworkDisplayName = ".NET 8.0")]

backend/tests/FiscalFlow.UnitTests/obj/Debug/net8.0/InvoiceMaster.UnitTests.AssemblyInfo.cs

@@ -0,0 +1,22 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+using System;
+using System.Reflection;
+
+[assembly: System.Reflection.AssemblyCompanyAttribute("InvoiceMaster.UnitTests")]
+[assembly: System.Reflection.AssemblyConfigurationAttribute("Debug")]
+[assembly: System.Reflection.AssemblyFileVersionAttribute("1.0.0.0")]
+[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+05ea67144f6a97e372ca4293ce2393e15a3f6bb7")]
+[assembly: System.Reflection.AssemblyProductAttribute("InvoiceMaster.UnitTests")]
+[assembly: System.Reflection.AssemblyTitleAttribute("InvoiceMaster.UnitTests")]
+[assembly: System.Reflection.AssemblyVersionAttribute("1.0.0.0")]
+
+// Generated by the MSBuild WriteCodeFragment class.
+

backend/tests/FiscalFlow.UnitTests/obj/Debug/net8.0/InvoiceMaster.UnitTests.AssemblyInfoInputs.cache

@@ -0,0 +1 @@
+c077d4836482878dfcee69c0e412646849a04e73aee8bbed7559e6bb4a662308

backend/tests/FiscalFlow.UnitTests/obj/Debug/net8.0/InvoiceMaster.UnitTests.GeneratedMSBuildEditorConfig.editorconfig

@@ -0,0 +1,17 @@
+is_global = true
+build_property.TargetFramework = net8.0
+build_property.TargetFrameworkIdentifier = .NETCoreApp
+build_property.TargetFrameworkVersion = v8.0
+build_property.TargetPlatformMinVersion = 
+build_property.UsingMicrosoftNETSdkWeb = 
+build_property.ProjectTypeGuids = 
+build_property.InvariantGlobalization = 
+build_property.PlatformNeutralAssembly = 
+build_property.EnforceExtendedAnalyzerRules = 
+build_property._SupportedPlatformList = Linux,macOS,Windows
+build_property.RootNamespace = InvoiceMaster.UnitTests
+build_property.ProjectDir = C:\Users\yaoji\git\ColaCoder\accounting-system\backend\tests\InvoiceMaster.UnitTests\
+build_property.EnableComHosting = 
+build_property.EnableGeneratedComInterfaceComImportInterop = 
+build_property.EffectiveAnalysisLevelStyle = 8.0
+build_property.EnableCodeStyleSeverity = 

backend/tests/FiscalFlow.UnitTests/obj/Debug/net8.0/InvoiceMaster.UnitTests.GlobalUsings.g.cs

@@ -0,0 +1,8 @@
+// <auto-generated/>
+global using System;
+global using System.Collections.Generic;
+global using System.IO;
+global using System.Linq;
+global using System.Net.Http;
+global using System.Threading;
+global using System.Threading.Tasks;