[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.Tests/AcceptanceCriteriaRT2Tests.cs

@@ -0,0 +1,40 @@
+using FluentAssertions;
+
+namespace SatelliteProvider.Tests;
+
+public class AcceptanceCriteriaRT2Tests
+{
+    [Fact]
+    public void RT2_LinesAllFourPointTypes_AZ370_AC3()
+    {
+        var path = LocateAcceptanceCriteriaMd();
+        if (path is null)
+        {
+            Assert.Fail("acceptance_criteria.md not found from test runtime — repo layout drift");
+        }
+
+        var content = File.ReadAllText(path);
+        var rt2Line = content.Split('\n').FirstOrDefault(line => line.Contains("| RT2 |"));
+
+        rt2Line.Should().NotBeNull("RT2 row must exist in the Route Management section");
+        rt2Line!.Should().Contain("\"start\"");
+        rt2Line.Should().Contain("\"end\"");
+        rt2Line.Should().Contain("\"action\"");
+        rt2Line.Should().Contain("\"intermediate\"");
+    }
+
+    private static string? LocateAcceptanceCriteriaMd()
+    {
+        var dir = new DirectoryInfo(Directory.GetCurrentDirectory());
+        while (dir is not null)
+        {
+            var candidate = Path.Combine(dir.FullName, "_docs", "00_problem", "acceptance_criteria.md");
+            if (File.Exists(candidate))
+            {
+                return candidate;
+            }
+            dir = dir.Parent;
+        }
+        return null;
+    }
+}