chore: Bump Azure.Security.KeyVault.Secrets from 4.7.0 to 4.8.0

---
updated-dependencies:
- dependency-name: Azure.Security.KeyVault.Secrets
  dependency-version: 4.8.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Directory.Packages.props

@@ -34,7 +34,7 @@
     <PackageVersion Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="9.0.6" />
     <!-- Replace vulnerable AzureKeyVault package with modern Azure SDK -->
     <PackageVersion Include="Azure.Extensions.AspNetCore.Configuration.Secrets" Version="1.4.0" />
-    <PackageVersion Include="Azure.Security.KeyVault.Secrets" Version="4.7.0" />
+    <PackageVersion Include="Azure.Security.KeyVault.Secrets" Version="4.8.0" />
     <PackageVersion Include="Azure.Identity" Version="1.14.0" />
     <!-- Validation -->
     <PackageVersion Include="FluentValidation" Version="12.0.0" />