feat: implement central package management and stabilize mobile build (#50)

This pull request implements **Central Package Management (CPM)** across the NexusReader solution to centralize package version definitions, improve package maintainability, and ensure security patch consistency. It also resolves compile issues in the mobile infrastructure and client projects.

### Key Changes

#### 1. NuGet Central Package Management (CPM)
- Created `Directory.Packages.props` in the solution root containing all solution-wide dependency versions (consolidating 48 packages).
- Pinned and secured `Microsoft.Bcl.Memory` to `v9.0.14` to resolve a known high-severity vulnerability (CVE-2026-26127).
- Stripped explicit `Version` attributes from `.csproj` files for the core library, web client, web host, UI shared, data access, and testing projects to inherit central version definitions.

#### 2. Mobile / MAUI Projects Stabilization
- **Workload Support & Locally Disabled CPM**: Disabled Central Package Management locally (`<ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>`) in both `NexusReader.Infrastructure.Mobile.csproj` and `NexusReader.Maui.csproj` to preserve native MAUI workload package integration while cleanly referencing package versions manually.
- **Ambiguity Resolving**: Added using aliases for `FluentResults.Result` to eliminate compiler ambiguity conflicts between `Android.App.Result` and `FluentResults.Result` inside Android platform service implementations.
- **Missing Namespaces Fix**: Added explicit hosting imports (`using Microsoft.Maui; using Microsoft.Maui.Hosting;`) and ensured `Microsoft.Maui.Essentials` references resolve properly in the mobile context.

---

### Verification
- **Build**: Successfully built the entire solution with zero compilation errors (`dotnet build NexusReader.slnx --no-restore` -> `Liczba błędów: 0`).
- **Tests**: All 7 integration and unit tests run and pass successfully (`dotnet test NexusReader.slnx --no-restore`).

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #50
Reviewed-by: Marek Jaisński <jasins.marek@gmail.com>
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

src/NexusReader.Infrastructure.Mobile/NexusReader.Infrastructure.Mobile.csproj

@@ -5,13 +5,19 @@
     <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('osx'))">$(TargetFrameworks);net10.0-ios;net10.0-maccatalyst</TargetFrameworks>
     <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net10.0-windows10.0.19041.0</TargetFrameworks>
     <UseMaui>true</UseMaui>
+    <UseMauiEssentials>true</UseMauiEssentials>
     <SkipValidateMauiImplicitPackageReferences>true</SkipValidateMauiImplicitPackageReferences>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
+    <ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>
   </PropertyGroup>
 
   <ItemGroup>
     <ProjectReference Include="..\NexusReader.Application\NexusReader.Application.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Maui.Essentials" Version="10.0.20" />
+  </ItemGroup>
+
 </Project>

src/NexusReader.Infrastructure.Mobile/Services/MauiPlatformService.cs

@@ -1,4 +1,5 @@
 using FluentResults;
+using Result = FluentResults.Result;
 using Microsoft.Maui.Devices;
 using NexusReader.Application.Abstractions.Services;
 

src/NexusReader.Infrastructure.Mobile/Services/MauiStorageService.cs

@@ -1,4 +1,5 @@
 using FluentResults;
+using Result = FluentResults.Result;
 using Microsoft.Maui.Storage;
 using NexusReader.Application.Abstractions.Services;