[AZ-493] Cycle 3 batch 3: integration test DB-reset hook

AZ-493 (2 SP): replace the cycle-2 wallclock-seeded _coordinateCounter
workaround with a proper Postgres state-reset hook that runs at
integration test runner startup, eliminating the per-source-unique-index
collision risk that the persistent docker-compose Postgres volume
introduced post-AZ-484.

The reset is split into two surfaces:

* SatelliteProvider.TestSupport.IntegrationTestResetGuard - pure
  static class, I/O-free, unit-tested. Two independent guards: (a)
  ASPNETCORE_ENVIRONMENT must equal "Testing", (b) DB_CONNECTION_STRING
  Host must be in the allowed-host list (postgres, localhost, 127.0.0.1).
  Failure of either guard surfaces a structured operator-friendly
  InvalidOperationException.
* SatelliteProvider.IntegrationTests.IntegrationTestDatabaseReset -
  instance class owning the Npgsql side effects. Calls the guard then
  runs TRUNCATE TABLE route_regions, route_points, routes, regions,
  tiles RESTART IDENTITY CASCADE inside a single Npgsql transaction.

Spec-vs-reality: the task spec prescribed "DB name contains _test" as
Guard 2; the actual compose file uses Database=satelliteprovider and
DB rename is gated on user confirmation per coderule.mdc. Substituted
a Host allowlist as the equivalent guard (intent identical: reject
remote / production hosts). Recorded as Low/Spec-Gap in the review.

Program.cs adds --keep-state CLI flag and INTEGRATION_KEEP_STATE env
var (1/true) opt-outs so a developer can inspect leftover state when
debugging. Startup banner shows which path executed.
docker-compose.tests.yml gets ASPNETCORE_ENVIRONMENT=Testing +
passthrough for INTEGRATION_KEEP_STATE. scripts/run-tests.sh wires the
--keep-state flag through to compose.

UavUploadTests._coordinateCounter wallclock seed is retained as
defense-in-depth (per the task spec's implementer choice). The reset
is the primary isolation path; the seed is the belt-and-suspenders
fallback for --keep-state runs.

8 new unit tests in SatelliteProvider.Tests/TestSupport/
IntegrationTestResetGuardTests.cs cover Production/Staging/missing-env
throw, allowed-host case-insensitivity, disallowed-host rejection
with representative prod hostnames, and the AllowedHosts contract.

tests_integration.md gains a Reliability section that documents the
hook, the two guards, the truncate order, and the three opt-out forms.
module-layout.md TestSupport entry extended with the new pure guard
and the explicit "Npgsql stays in IntegrationTests" boundary.

Test-suite gate (AC-6) deferred to Step 16 Final Test Run per implement
skill convention. Per-batch review verdict: PASS_WITH_WARNINGS with 1
Low (spec-vs-reality on Guard 2, non-blocking).

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

_docs/02_document/module-layout.md

@@ -164,16 +164,18 @@ 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)
+### TestSupport (added by AZ-491; extended by AZ-493)
 
 - **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).
+- **Purpose**: Canonical home for cross-project test utilities. Currently holds `JwtTokenFactory` (HS256 token minting + signature tampering) and `IntegrationTestResetGuard` (pure-string guard for the integration-test DB-reset hook). 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`) — added by AZ-491.
+  - `SatelliteProvider.TestSupport/IntegrationTestResetGuard.cs` (`EnsureGuardPassesOrThrow`, `AllowedHosts`, `EnvironmentEnvVar`, `TestingEnvironment`) — added by AZ-493. Pure static class — no I/O, no DB calls. Consumed by `SatelliteProvider.IntegrationTests/IntegrationTestDatabaseReset.cs` (instance class that owns the Npgsql side effects) and unit-tested in `SatelliteProvider.Tests/TestSupport/IntegrationTestResetGuardTests.cs`.
+- **PackageReferences**: `Microsoft.IdentityModel.Tokens` 7.0.3, `System.IdentityModel.Tokens.Jwt` 7.0.3 (matches the integration tests' pre-AZ-491 explicit reference). The AZ-493 guard introduced no new package dependencies — it is pure string comparison over the BCL.
 - **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.
+- **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. `SatelliteProvider.IntegrationTests/IntegrationTestDatabaseReset.cs` (AZ-493) holds the Npgsql side effects of the reset — it sits in the integration-tests project (not TestSupport) so the Npgsql dependency doesn't leak into unit tests.
 
 ## Allowed Dependencies (layering)