[AZ-373] Refactor C20: drop MapsVersion from new writes (option a)

- Stop writing "downloaded_YYYY-MM-DD" into tiles.maps_version: new rows
  bind @MapsVersion to NULL via TileService.BuildTileEntity.
- Retain the tiles.maps_version column (coderule.mdc forbids unprompted
  column drops); pre-existing rows keep their values for forensics.
- Remove MapsVersion property from DownloadTileResponse (API wire shape)
  and TileMetadata (internal DTO); OpenAPI schema regenerates from the
  DTO via Swashbuckle.
- Add 3 AC tests in TileServiceTests covering the captured-entity write
  (AC-1) and the DTO/wire-shape removal (AC-2).
- Update integration-test local DTO + console output; refresh docs in
  common_dtos.md, services_tile_service.md, data_model.md.
- Archive AZ-373 task file: todo/ -> done/.

174 unit + 5 smoke pass.

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

_docs/02_document/modules/common_dtos.md

@@ -30,7 +30,7 @@ Represents a single map tile with its spatial bounds.
 Metadata about a stored tile (mirrors `TileEntity` but without DB-specific concerns).
 - `Id` (Guid), `TileZoom`, `TileX`, `TileY` (int), `Latitude`, `Longitude` (double)
 - `TileSizeMeters` (double), `TileSizePixels` (int), `ImageType` (string)
-- `MapsVersion` (string?), `Version` (int), `FilePath` (string)
+- `Version` (int?), `FilePath` (string)
 - `CreatedAt`, `UpdatedAt` (DateTime)
 
 ### RegionRequest