[AZ-484] Fix multi-source tile reads: drop Dapper enum handler

Two integration-test failures uncovered after the initial commit:

1) GetTilesByRegionAsync outer ORDER BY referenced 'updated_at' but
   the inner DISTINCT ON subquery aliased it to 'UpdatedAt' (Postgres
   folds to 'updatedat'). DISTINCT ON already guarantees one row per
   (latitude, longitude, ...) so the third tiebreak was unreachable;
   removed it.

2) Dapper 2.1.35 silently bypasses SqlMapper.TypeHandler<T> for enum
   types during read deserialization (Dapper issue #259). The
   TileSourceTypeHandler worked for writes but reads fell through to
   Enum.TryParse, which cannot map 'google_maps' to GoogleMaps.

   Pivoted: TileEntity.Source is now a string (the wire value).
   TileSource enum stays as the public producer surface in
   Common.Enums; TileSourceConverter (Common.Enums) provides
   ToWireValue / FromWireValue / IsValidWireValue at the boundary.
   TileSourceTypeHandler deleted; registration removed from
   DapperEnumTypeHandlers.RegisterAll.

   tile-storage.md Inv-5 amended to document the storage choice.
   _docs/LESSONS.md L-001 records the Dapper bypass for future cycles.

Full suite passes (213 unit + integration suite incl. AZ-484
AC-1..AC-5, security SEC-01..SEC-04, AZ-356/362/357).

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

SatelliteProvider.Tests/TileSourceConverterTests.cs

@@ -0,0 +1,81 @@
+using FluentAssertions;
+using SatelliteProvider.Common.Enums;
+
+namespace SatelliteProvider.Tests;
+
+public class TileSourceConverterTests
+{
+    [Theory]
+    [InlineData(TileSource.GoogleMaps, "google_maps")]
+    [InlineData(TileSource.Uav, "uav")]
+    public void ToWireValue_EmitsContractWireValue_AZ484(TileSource value, string expected)
+    {
+        // Act
+        var result = TileSourceConverter.ToWireValue(value);
+
+        // Assert
+        result.Should().Be(expected);
+    }
+
+    [Theory]
+    [InlineData("google_maps", TileSource.GoogleMaps)]
+    [InlineData("GOOGLE_MAPS", TileSource.GoogleMaps)]
+    [InlineData("uav", TileSource.Uav)]
+    [InlineData("UAV", TileSource.Uav)]
+    public void FromWireValue_AcceptsContractWireValue_AZ484(string raw, TileSource expected)
+    {
+        // Act
+        var result = TileSourceConverter.FromWireValue(raw);
+
+        // Assert
+        result.Should().Be(expected);
+    }
+
+    [Theory]
+    [InlineData(TileSource.GoogleMaps)]
+    [InlineData(TileSource.Uav)]
+    public void RoundTrip_PreservesValue_AZ484(TileSource value)
+    {
+        // Act
+        var roundTripped = TileSourceConverter.FromWireValue(TileSourceConverter.ToWireValue(value));
+
+        // Assert
+        roundTripped.Should().Be(value);
+    }
+
+    [Fact]
+    public void FromWireValue_UnknownString_ThrowsArgumentException_AZ484()
+    {
+        // Act
+        Action act = () => TileSourceConverter.FromWireValue("satar");
+
+        // Assert — Inv-1: unknown sources surface, not silently coerce (coderule.mdc: never suppress errors).
+        act.Should().Throw<ArgumentException>().WithMessage("*satar*");
+    }
+
+    [Fact]
+    public void FromWireValue_NullValue_ThrowsArgumentNullException_AZ484()
+    {
+        // Act
+        Action act = () => TileSourceConverter.FromWireValue(null!);
+
+        // Assert
+        act.Should().Throw<ArgumentNullException>();
+    }
+
+    [Theory]
+    [InlineData("google_maps", true)]
+    [InlineData("uav", true)]
+    [InlineData("GoogleMaps", false)]
+    [InlineData("satar", false)]
+    [InlineData("", false)]
+    [InlineData(null, false)]
+    public void IsValidWireValue_OnlyExactWireValuesPass_AZ484(string? raw, bool expected)
+    {
+        // Act
+        var result = TileSourceConverter.IsValidWireValue(raw);
+
+        // Assert
+        result.Should().Be(expected);
+    }
+}