[AZ-351][AZ-352][AZ-363] Refactor 03 batch 1: critical defensive fixes

AZ-351: Resolve ILogger<DatabaseMigrator> directly from DI in
Program.cs instead of casting ILogger<Program> (which always
returned null). Migrator now logs through Serilog at startup.

AZ-352: Drop empty catch in
RouteProcessingService.ExtractTileCoordinatesFromFilename. Convert
the method from private static to internal instance so it can use
the existing _logger (per coderule: side-effecting code must not be
static). Add typed null-guard via ArgumentNullException.ThrowIfNull
so unexpected exceptions propagate. Adds InternalsVisibleTo on the
RouteManagement csproj for SatelliteProvider.Tests, plus 4 unit
tests in RouteProcessingServiceTests.cs covering AC-1 (valid /
malformed / non-numeric) and AC-2 (null path propagation).

AZ-363: Delete _totalEnqueued / _totalDequeued fields and the two
non-atomic ++ writes in RegionRequestQueue. Fields were write-only
dead code and a thread-safety hazard.

Tests: 44/44 unit + 5/5 smoke (scripts/run-tests.sh --smoke).
Code review verdict: PASS, 0 findings, 0 auto-fix attempts.
Batch report: _docs/03_implementation/batch_07_report.md.

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

SatelliteProvider.Services.RegionProcessing/RegionRequestQueue.cs

@@ -9,8 +9,6 @@ public class RegionRequestQueue : IRegionRequestQueue
 {
     private readonly Channel<RegionRequest> _queue;
     private readonly ILogger<RegionRequestQueue>? _logger;
-    private int _totalEnqueued = 0;
-    private int _totalDequeued = 0;
 
     public RegionRequestQueue(int capacity, ILogger<RegionRequestQueue>? logger = null)
     {
@@ -25,7 +23,6 @@ public class RegionRequestQueue : IRegionRequestQueue
 
     public async ValueTask EnqueueAsync(RegionRequest request, CancellationToken cancellationToken = default)
     {
-        _totalEnqueued++;
         await _queue.Writer.WriteAsync(request, cancellationToken);
     }
 
@@ -35,7 +32,6 @@ public class RegionRequestQueue : IRegionRequestQueue
         {
             if (_queue.Reader.TryRead(out var request))
             {
-                _totalDequeued++;
                 return request;
             }
         }