[AZ-370] Refactor C17: status / point-type enums + AC RT2 update

Replaces bare strings with two enums in Common/Enums/:
  RegionStatus { Queued, Processing, Completed, Failed }
  RoutePointType { Start, End, Action, Intermediate }

Adds a Dapper EnumStringTypeHandler<T> (DataAccess/TypeHandlers/)
that round-trips enums to/from lowercase strings, registered once
at startup via DapperEnumTypeHandlers.RegisterAll(). DataAccess now
references Common (project ref) so entities can carry the enum types.

Sites converted: RegionService (5), RouteProcessingService (3),
RoutePointGraphBuilder (4), entity Status/PointType columns. Log
message and summary file format preserved via .ToLowerInvariant().

API JSON contract preserved by adding JsonStringEnumConverter with
JsonNamingPolicy.CamelCase to the http JSON options — single-word
enum members serialize to the same lowercase strings as before.

DTO renamed: Common.DTO.RegionStatus -> RegionStatusResponse to
free the RegionStatus name for the new enum (forced by the task's
explicit enum name); the renamed DTO has no public-API impact at
the JSON wire level. Stale doc references updated.

AC RT2 in _docs/00_problem/acceptance_criteria.md now lists all 4
point types (start/end/action/intermediate).

Tests: 171 / 171 unit + 5 / 5 smoke green (was 141 + 5; +30 new tests
covering type handler round-trip, set/parse, unknown-value rejection,
idempotent registration, and the AC RT2 doc check).

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

SatelliteProvider.Services.RegionProcessing/RegionService.cs

@@ -2,6 +2,7 @@ using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using SatelliteProvider.Common.Configs;
 using SatelliteProvider.Common.DTO;
+using SatelliteProvider.Common.Enums;
 using SatelliteProvider.Common.Exceptions;
 using SatelliteProvider.Common.Imaging;
 using SatelliteProvider.Common.Interfaces;
@@ -38,7 +39,7 @@ public class RegionService : IRegionService
         _logger = logger;
     }
 
-    public async Task<RegionStatus> RequestRegionAsync(Guid id, double latitude, double longitude, double sizeMeters, int zoomLevel, bool stitchTiles = false)
+    public async Task<RegionStatusResponse> RequestRegionAsync(Guid id, double latitude, double longitude, double sizeMeters, int zoomLevel, bool stitchTiles = false)
     {
         // AZ-362: idempotent POST contract. A retried POST with the same caller-supplied
         // Id returns the existing region instead of bubbling a unique-key violation.
@@ -47,7 +48,7 @@ public class RegionService : IRegionService
         {
             _logger.LogInformation(
                 "Idempotent region POST: id {RegionId} already exists with status {Status}; returning existing resource without re-enqueueing",
-                id, existing.Status);
+                id, existing.Status.ToString().ToLowerInvariant());
             return MapToStatus(existing);
         }
 
@@ -60,7 +61,7 @@ public class RegionService : IRegionService
             SizeMeters = sizeMeters,
             ZoomLevel = zoomLevel,
             StitchTiles = stitchTiles,
-            Status = "queued",
+            Status = RegionStatus.Queued,
             TilesDownloaded = 0,
             TilesReused = 0,
             CreatedAt = now,
@@ -84,7 +85,7 @@ public class RegionService : IRegionService
         return MapToStatus(region);
     }
 
-    public async Task<RegionStatus?> GetRegionStatusAsync(Guid id)
+    public async Task<RegionStatusResponse?> GetRegionStatusAsync(Guid id)
     {
         var region = await _regionRepository.GetByIdAsync(id);
         return region != null ? MapToStatus(region) : null;
@@ -101,7 +102,7 @@ public class RegionService : IRegionService
             return;
         }
 
-        region.Status = "processing";
+        region.Status = RegionStatus.Processing;
         region.UpdatedAt = DateTime.UtcNow;
         await _regionRepository.UpdateAsync(region);
 
@@ -151,7 +152,7 @@ public class RegionService : IRegionService
             
             await GenerateSummaryFileAsync(summaryPath, id, region, tiles, tilesDownloaded, tilesReused, stitchedImagePath, processingStartTime, linkedCts.Token, errorMessage);
 
-            region.Status = "completed";
+            region.Status = RegionStatus.Completed;
             region.CsvFilePath = csvPath;
             region.SummaryFilePath = summaryPath;
             region.TilesDownloaded = tilesDownloaded;
@@ -182,7 +183,7 @@ public class RegionService : IRegionService
         int tilesReused,
         string errorMessage)
     {
-        region.Status = "failed";
+        region.Status = RegionStatus.Failed;
         region.UpdatedAt = DateTime.UtcNow;
         
         try
@@ -311,7 +312,7 @@ public class RegionService : IRegionService
         summary.AppendLine($"Center: {region.Latitude:F6}, {region.Longitude:F6}");
         summary.AppendLine($"Size: {region.SizeMeters:F0} meters");
         summary.AppendLine($"Zoom Level: {region.ZoomLevel}");
-        summary.AppendLine($"Status: {region.Status}");
+        summary.AppendLine($"Status: {region.Status.ToString().ToLowerInvariant()}");
         summary.AppendLine();
         
         if (!string.IsNullOrEmpty(errorMessage))
@@ -328,7 +329,7 @@ public class RegionService : IRegionService
         summary.AppendLine($"- Processing Time: {processingTime:F2} seconds");
         summary.AppendLine($"- Started: {startTime:yyyy-MM-dd HH:mm:ss} UTC");
         
-        if (region.Status == "completed")
+        if (region.Status == RegionStatus.Completed)
         {
             summary.AppendLine($"- Completed: {endTime:yyyy-MM-dd HH:mm:ss} UTC");
         }
@@ -356,9 +357,9 @@ public class RegionService : IRegionService
         await File.WriteAllTextAsync(filePath, summary.ToString(), cancellationToken);
     }
 
-    private static RegionStatus MapToStatus(RegionEntity region)
+    private static RegionStatusResponse MapToStatus(RegionEntity region)
     {
-        return new RegionStatus
+        return new RegionStatusResponse
         {
             Id = region.Id,
             Status = region.Status,