[AZ-808] [AZ-811] Strict validation on region POST + lat/lon GET

AZ-808: FluentValidation for POST /api/satellite/request
- RegionRequestValidator: id non-empty, lat/lon/sizeMeters/zoomLevel ranges
- RequestRegionRequest: [JsonRequired] on every property, no implicit defaults
- Wired via .WithValidation<RequestRegionRequest>() in MapPost chain
- Unit + integration tests + curl probe script
- New contract: contracts/api/region-request.md v1.0.0

AZ-811: FluentValidation + envelope filter for GET /api/satellite/tiles/latlon
- GetTileByLatLonQuery: nullable record (double?/int?) so the minimal-API
  binder never short-circuits with BadHttpRequestException before filters
- GetTileByLatLonQueryValidator: Cascade(Stop) + NotNull + InclusiveBetween
  per param; missing surfaces as `\`<name>\` is required.`
- RejectUnknownQueryParamsEndpointFilter: reusable IEndpointFilter that
  rejects any query key outside the allowed set with errors[<key>] map;
  catches legacy `?Latitude=` typos and hostile probes (`?debug=1&admin=1`)
- Handler: [AsParameters] GetTileByLatLonQuery + .Value deref post-validator
- Unit (validator + filter) + integration tests + curl probe script
- New contract: contracts/api/tile-latlon.md v1.0.0

Shared hygiene
- Promote AssertErrorsContainsMention from per-test-file private helpers to
  ProblemDetailsAssertions (closes batch-1 Low-severity DRY warning)
- Sync Swagger param descriptions, README, blackbox/security/perf scripts,
  uuidv5 doc with the new lat/lon/zoom query-param names

Docs
- system-flows.md F1/F2 reference the new contracts + validation layers
- modules/api_program.md adds Api/Validators + Api/DTOs sections
- _autodev_state.md: batch 2 of 4 complete; next batch = AZ-809

All smoke tests green (mode=smoke, exit 0). AZ-808 + AZ-811 transitioned
to In Testing on Jira.

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

SatelliteProvider.Api/DTOs/GetTileByLatLonQuery.cs

@@ -0,0 +1,26 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace SatelliteProvider.Api.DTOs;
+
+// AZ-811: query-string record for GET /api/satellite/tiles/latlon.
+// Bound via `[AsParameters]` so each property maps to one query parameter.
+// `[FromQuery(Name = "...")]` pins the wire name explicitly — case-sensitive
+// match against `?lat=&lon=&zoom=`, matching the OSM convention shared with
+// the rest of the satellite-provider API (`{z, x, y}` for inventory,
+// `{lat, lon}` for region and route DTOs).
+//
+// **Why nullable types**: minimal-API parameter binding throws
+// BadHttpRequestException for missing-required non-nullable query params
+// BEFORE endpoint filters run. That short-circuit produces a plain
+// ProblemDetails via GlobalExceptionHandler — no `errors{}` envelope, no
+// per-field key. Per AZ-811 ACs 1 & 4 every missing/unknown param must
+// surface as `errors.<paramName>` in ValidationProblemDetails. Nullable
+// types let binding always succeed, so:
+//   1. RejectUnknownQueryParamsEndpointFilter handles unknown keys
+//      (e.g. legacy `?Latitude=`, hostile `?debug=1`).
+//   2. GetTileByLatLonQueryValidator handles `null` (missing) plus range.
+// Validator guarantees non-null by the time the handler dereferences.
+public sealed record GetTileByLatLonQuery(
+    [property: FromQuery(Name = "lat")] double? Lat,
+    [property: FromQuery(Name = "lon")] double? Lon,
+    [property: FromQuery(Name = "zoom")] int? Zoom);