build: update compatible CountryService dependencies

[natthapolvanasrivilai]

Outcome

Replaces the three standalone red Dependabot PRs (#36, #41, #42) and the independently compatible portion of grouped PR #40 with one current-base, locked dependency update.

Updated direct test dependencies

• coverlet.collector 6.0.2 -> 10.0.1
• xunit 2.9.2 -> 2.9.3
• xunit.runner.visualstudio 2.8.2 -> 3.1.5
• System.Drawing.Common 9.0.0 -> 10.0.10
• Azure.Identity 1.14.1 -> 1.21.0
• Microsoft test/ASP.NET test packages, Npgsql, JWT, and Testcontainers to the reviewed current versions proposed by Bump the nuget-minor-and-patch group with 21 updates #40
• regenerated and committed the exact test lockfile

Deliberate compatibility boundary

The EF Core/Microsoft.Extensions 10.0.10 portion of #40 is excluded: it produces MSB3277/CS1705 against the pinned public ServiceDefaults source, which is built on EF Core 10.0.5. That cross-service stack must move atomically in a separately reviewed shared-dependency change; this PR does not force a mixed assembly graph.

RED -> GREEN evidence

• RED: locked restore failed NU1004 against stale locks after direct-version changes.
• Locks regenerated from NuGet.org; locked restore then passed.
• A trial EF 10.0.10 stack failed build with MSB3277/CS1705 and was removed from this slice.
• Release build: 0 warnings, 0 errors.
• Full tests: 263/263 passed.
• Format, Actionlint, current-tree gitleaks: clean.
• Transitive vulnerability audit: no vulnerable packages.

Safety boundary

Test/development dependencies and their lockfile only. No runtime route/DTO/schema change, deployment, image publication, GitOps/environment write, or database operation.