Bump Microsoft.Identity.Web from 4.7.0 to 4.9.0

---
updated-dependencies:
- dependency-name: Microsoft.Identity.Web
  dependency-version: 4.9.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/Backend/Backend.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="10.0.7" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.7" />
     <PackageReference Include="Microsoft.Identity.Web.DownstreamApi" Version="4.8.0" />
-    <PackageReference Include="Microsoft.Identity.Web" Version="4.7.0" />
+    <PackageReference Include="Microsoft.Identity.Web" Version="4.9.0" />
   </ItemGroup>
 
 </Project>