[AZ-491] Cycle 3 batch 2: consolidate JWT test-mint helpers into TestSupport

AZ-491 (3 SP): eliminate the cycle-2 duplicate of JWT-minting logic
that existed in both SatelliteProvider.Tests/TestUtilities/
JwtTokenFactory.cs (unit-side) and SatelliteProvider.IntegrationTests/
JwtTestHelpers.cs (integration-side), where the same Expires <
NotBefore bug needed parallel fixes in commits f64d0d7 + 11b7074.

Option A chosen: new SatelliteProvider.TestSupport class library
(no test framework) holds the canonical JwtTokenFactory.Create /
CreateExpired / TamperSignature. Both Tests and IntegrationTests
consume it via ProjectReference; production projects (Api, Common,
DataAccess, Services.*) cannot depend on it. The notBefore-shift
workaround is preserved with an inline regression-prevention comment
back-referencing the cycle-2 fix commits.

SatelliteProvider.IntegrationTests/JwtTestHelpers.cs is stripped to
runner-only concerns: ResolveSecretOrThrow, AttachDefaultAuthorization,
and the DefaultSubject = "integration-tests" constant. Call sites in
Program.cs, JwtIntegrationTests.cs, and UavUploadTests.cs (10 sites)
switched to JwtTokenFactory.* with JwtTestHelpers.DefaultSubject
explicitly passed for the runner subject - behavior parity preserved.

Dockerfile for IntegrationTests gets the new TestSupport csproj
in its pre-restore COPY layer. Api Dockerfile unchanged (TestSupport
is NOT a production dependency).

A new code-review SKILL.md Phase 6 checklist row flags near-identical
helper logic across test projects as a Medium / Maintainability
finding with explicit cycle-2 retro back-reference, so this whole
pattern stops at one occurrence.

module-layout.md adds a TestSupport Shared/Cross-Cutting entry
documenting the production-isolation invariant. tests_unit.md +
tests_integration.md updated to describe the consolidated layout.
sln updated.

Test-suite gate (AC-2 + AC-3) deferred to Step 16 Final Test Run
per implement-skill convention. Per-batch review verdict:
PASS_WITH_WARNINGS with 1 Low (pre-existing 7.0.3 version pin
preserved verbatim from cycle-2 IntegrationTests csproj for parity;
not blocking; deferred bump).

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/02_document/modules/tests_unit.md

@@ -24,7 +24,7 @@ Existing baseline (pre-cycle-2) test classes cover `TileService`, `RegionService
 - `JwtSecurityTokenHandler.MapInboundClaims = false` is set explicitly in JWT tests so claims read by their original names (`sub`, `permissions`, …) rather than the framework-remapped names.
 
 ## Dependencies
-- Project references: `SatelliteProvider.Services.TileDownloader`, `SatelliteProvider.Services.RegionProcessing`, `SatelliteProvider.Services.RouteManagement`, `SatelliteProvider.Common`, `SatelliteProvider.DataAccess`, `SatelliteProvider.Api` (for the Authentication tests — added in AZ-487).
+- Project references: `SatelliteProvider.Services.TileDownloader`, `SatelliteProvider.Services.RegionProcessing`, `SatelliteProvider.Services.RouteManagement`, `SatelliteProvider.Common`, `SatelliteProvider.DataAccess`, `SatelliteProvider.Api` (for the Authentication tests — added in AZ-487), `SatelliteProvider.TestSupport` (added by AZ-491; provides the canonical `JwtTokenFactory` consumed by both this project and `SatelliteProvider.IntegrationTests`).
 - NuGet: xUnit (2.5.3), Moq (4.20.72), FluentAssertions (8.8.0), coverlet.collector (6.0.0), Microsoft.NET.Test.Sdk (17.8.0), Microsoft.Extensions.* (Caching.Memory, Configuration, DI, Logging, Options, Http), `Microsoft.AspNetCore.Authentication.JwtBearer` 8.0.25 (consumed transitively via the `ProjectReference` to `SatelliteProvider.Api`; AZ-487 added the dependency at 8.0.21, AZ-496 bumped it to 8.0.25), `SixLabors.ImageSharp` 3.1.11 (added by AZ-488 for the gate tests).
 - `appsettings.json` copied to output (used by Authentication tests for the `Jwt` section binding scenario).