[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/Program.cs

@@ -206,6 +206,10 @@ app.MapGet("/tiles/{z:int}/{x:int}/{y:int}", ServeTile)
 
 app.MapGet("/api/satellite/tiles/latlon", GetTileByLatLon)
     .RequireAuthorization()
+    .AddEndpointFilter(new RejectUnknownQueryParamsEndpointFilter(new[] { "lat", "lon", "zoom" }))
+    .WithValidation<GetTileByLatLonQuery>()
+    .Produces<DownloadTileResponse>(StatusCodes.Status200OK)
+    .ProducesProblem(StatusCodes.Status400BadRequest)
     .WithOpenApi(op => new(op) { Summary = "Get satellite tile by latitude and longitude coordinates" });
 
 app.MapGet("/api/satellite/tiles/mgrs", GetSatelliteTilesByMgrs)
@@ -239,6 +243,10 @@ app.MapPost("/api/satellite/upload", UploadUavTileBatch)
 
 app.MapPost("/api/satellite/request", RequestRegion)
     .RequireAuthorization()
+    .WithValidation<RequestRegionRequest>()
+    .Accepts<RequestRegionRequest>("application/json")
+    .Produces<RegionStatusResponse>(StatusCodes.Status200OK)
+    .ProducesProblem(StatusCodes.Status400BadRequest)
     .WithOpenApi(op => new(op)
     {
         Summary = "Request tiles for a region",
@@ -271,9 +279,11 @@ async Task<IResult> ServeTile(int z, int x, int y, HttpContext httpContext, ITil
     return Results.Bytes(tile.Bytes, tile.ContentType);
 }
 
-async Task<IResult> GetTileByLatLon([FromQuery] double Latitude, [FromQuery] double Longitude, [FromQuery] int ZoomLevel, HttpContext httpContext, ITileService tileService)
+async Task<IResult> GetTileByLatLon([AsParameters] GetTileByLatLonQuery query, HttpContext httpContext, ITileService tileService)
 {
-    var tile = await tileService.DownloadAndStoreSingleTileAsync(Latitude, Longitude, ZoomLevel, httpContext.RequestAborted);
+    // AZ-811: GetTileByLatLonQueryValidator guarantees lat/lon/zoom are non-null
+    // by the time the handler runs (CascadeMode.Stop + NotNull rules).
+    var tile = await tileService.DownloadAndStoreSingleTileAsync(query.Lat!.Value, query.Lon!.Value, query.Zoom!.Value, httpContext.RequestAborted);
 
     var response = new DownloadTileResponse
     {
@@ -341,11 +351,6 @@ async Task<IResult> UploadUavTileBatch(
 
 async Task<IResult> RequestRegion([FromBody] RequestRegionRequest request, IRegionService regionService)
 {
-    if (request.SizeMeters < 100 || request.SizeMeters > 10000)
-    {
-        return Results.BadRequest(new { error = "Size must be between 100 and 10000 meters" });
-    }
-
     var status = await regionService.RequestRegionAsync(
         request.Id,
         request.Lat,