[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/module-layout.md

@@ -164,6 +164,17 @@ The cycle-1 (AZ-487) and cycle-2 (AZ-488) code reviews each surfaced an F1 (Low
 - **Consumed by**: DataAccess (entity defaults, type handler registration), TileDownloader (sets `TileEntity.Source` via `TileSourceConverter.ToWireValue`), Tests
 - **Important constraint**: Dapper's `SqlMapper.TypeHandler<TEnum>` is bypassed for enum reads (Dapper issue #259 — see `_docs/LESSONS.md` L-001). For any new enum that must round-trip through a database column, prefer the `string`-on-entity + `Enum`-at-API-boundary pattern with a converter class in this folder. Do NOT register a `TypeHandler<TEnum>` and assume it will be honored on reads.
 
+### TestSupport (added by AZ-491)
+
+- **Directory**: `SatelliteProvider.TestSupport/`
+- **csproj**: `SatelliteProvider.TestSupport/SatelliteProvider.TestSupport.csproj` (class library, no test framework)
+- **Purpose**: Canonical home for cross-project test utilities. Currently holds `JwtTokenFactory` (HS256 token minting + signature tampering). Replaces the cycle-2 duplicate that lived in both `SatelliteProvider.Tests/TestUtilities/JwtTokenFactory.cs` and `SatelliteProvider.IntegrationTests/JwtTestHelpers.cs` and required parallel fixes. Future additions: shared image-fixture factories, shared deterministic clocks / test-data builders that need to be visible to both unit and integration projects.
+- **Public API**: `SatelliteProvider.TestSupport/JwtTokenFactory.cs` (`Create`, `CreateExpired`, `TamperSignature`)
+- **PackageReferences**: `Microsoft.IdentityModel.Tokens` 7.0.3, `System.IdentityModel.Tokens.Jwt` 7.0.3 (matches the integration tests' pre-AZ-491 explicit reference).
+- **Consumed by**: `SatelliteProvider.Tests`, `SatelliteProvider.IntegrationTests` (both via `ProjectReference`).
+- **Not consumed by**: production projects (`Api`, `Common`, `DataAccess`, `Services.*`). The TestSupport library is test-only by design; production code must NOT depend on it.
+- **Runner-side concerns NOT in TestSupport**: `SatelliteProvider.IntegrationTests/JwtTestHelpers.cs` retains `ResolveSecretOrThrow`, `AttachDefaultAuthorization`, and the `DefaultSubject = "integration-tests"` constant — these are runner-specific (env-var reads, `HttpClient` mutation, runner-identity subject) and intentionally not consolidated.
+
 ## Allowed Dependencies (layering)
 
 | Layer | Components | May import from (compile-time ProjectReferences) |