[AZ-371] Refactor C18: magic numbers to ProcessingConfig/MapConfig

Promotes 8 operational levers into config keys with defaults that match
the prior source literals byte-for-byte:
  ProcessingConfig: RegionProcessingTimeoutSeconds (300),
  RouteProcessingPollIntervalSeconds (5),
  MaxRoutePointSpacingMeters (200), LatLonTolerance (0.0001).
  MapConfig: TileSizePixels (256), AllowedZoomLevels ([15..19]),
  RetryBaseDelaySeconds (1), RetryMaxDelaySeconds (30).

Sites updated: RegionService, RouteProcessingService,
RoutePointGraphBuilder, RouteValidator, RouteService 4-arg ctor,
RouteImageRenderer, GoogleMapsDownloaderV2, TileService. Closes LF-2 by
forwarding HttpContext.RequestAborted from GetTileByLatLon into the
downloader. appsettings.json gains the 8 new keys at default values.

Tests: 141 / 141 unit + 5 / 5 smoke green. New ConfigDefaultsTests pins
defaults to original literals; new TileService unit test asserts CT
identity from caller to downloader (AZ-371 AC-3).

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

SatelliteProvider.Services.RegionProcessing/RegionService.cs

@@ -19,6 +19,7 @@ public class RegionService : IRegionService
     private readonly IRegionRequestQueue _queue;
     private readonly ITileService _tileService;
     private readonly StorageConfig _storageConfig;
+    private readonly ProcessingConfig _processingConfig;
     private readonly ILogger<RegionService> _logger;
 
     public RegionService(
@@ -26,12 +27,14 @@ public class RegionService : IRegionService
         IRegionRequestQueue queue,
         ITileService tileService,
         IOptions<StorageConfig> storageConfig,
+        IOptions<ProcessingConfig> processingConfig,
         ILogger<RegionService> logger)
     {
         _regionRepository = regionRepository;
         _queue = queue;
         _tileService = tileService;
         _storageConfig = storageConfig.Value;
+        _processingConfig = processingConfig.Value;
         _logger = logger;
     }
 
@@ -102,7 +105,7 @@ public class RegionService : IRegionService
         region.UpdatedAt = DateTime.UtcNow;
         await _regionRepository.UpdateAsync(region);
 
-        using var timeoutCts = new CancellationTokenSource(TimeSpan.FromMinutes(5));
+        using var timeoutCts = new CancellationTokenSource(TimeSpan.FromSeconds(_processingConfig.RegionProcessingTimeoutSeconds));
         using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, timeoutCts.Token);
 
         string? errorMessage = null;