[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>

_docs/02_tasks/done/AZ-370_refactor_status_pointtype_enums.md

@@ -0,0 +1,73 @@
+# Refactor: status / point-type enums + acceptance_criteria.md RT2 update
+
+**Task**: AZ-370_refactor_status_pointtype_enums
+**Name**: Introduce RegionStatus + RoutePointType enums; sync AC RT2
+**Description**: Replace bare-string status / point-type values with enums; persist via Dapper type handler. Update AC RT2 wording to match the 4-value point-type reality.
+**Complexity**: 3 points
+**Dependencies**: None
+**Component**: Common + Services.RegionProcessing + Services.RouteManagement + Documentation
+**Tracker**: AZ-370
+**Epic**: AZ-350
+
+## Problem
+
+Status and point-type values are bare strings written to and compared from multiple sites: `RegionService.cs:49,90,140,209` ("queued"/"processing"/"completed"/"failed"), `RouteService.cs:66,100` and `RouteProcessingService.cs:138-140` ("start"/"end"/"action"/"intermediate"). Typos at compile time become runtime bugs. Acceptance criterion RT2 in `_docs/00_problem/acceptance_criteria.md` is also out of sync: it says point types are `original` / `intermediate`, but the lived code uses 4 values (`start` / `end` / `action` / `intermediate`).
+
+## Outcome
+
+- Two enums in `SatelliteProvider.Common/Enums/`: `RegionStatus { Queued, Processing, Completed, Failed }` and `RoutePointType { Start, End, Action, Intermediate }`.
+- All status / point-type compare and write sites use the enums.
+- Dapper persists them as the existing lowercase strings via a registered `EnumStringTypeHandler<T>`.
+- AC RT2 in `_docs/00_problem/acceptance_criteria.md` lists all 4 point types.
+- DB column types and stored values are identical; no migration needed.
+- 37 unit + 5 smoke tests stay green.
+
+## Scope
+
+### Included
+- Add the two enums.
+- Add a generic `EnumStringTypeHandler<T> : SqlMapper.TypeHandler<T>` and register both instantiations at startup.
+- Replace string-literal compare/write sites with enum values.
+- Update AC RT2 wording in `_docs/00_problem/acceptance_criteria.md`.
+- Add unit tests for the type handler (round-trip).
+
+### Excluded
+- Migrating existing rows (values are identical strings).
+- Renaming any column.
+- Adding any new status or point-type value.
+
+## Acceptance Criteria
+
+**AC-1: All compare/write sites use enums**
+Given the post-refactor source
+When grepped for `"queued"` / `"processing"` / `"completed"` / `"failed"` / `"start"` / `"end"` / `"action"` / `"intermediate"` as string literals in service code
+Then matches are confined to enum-value definitions and the type handler.
+
+**AC-2: DB round-trip preserves values**
+Given a row with `status = 'completed'` written by the new code
+When read back via Dapper
+Then it round-trips to `RegionStatus.Completed`.
+
+**AC-3: AC RT2 matches the code**
+Given the post-refactor `_docs/00_problem/acceptance_criteria.md`
+When RT2 is inspected
+Then it lists all 4 point types: `start`, `end`, `action`, `intermediate`.
+
+**AC-4: Tests stay green**
+Given the post-refactor build
+When `scripts/run-tests.sh --smoke` runs
+Then all 37 unit + 5 smoke scenarios pass.
+
+## Constraints
+
+- DB stored values unchanged (lowercase strings).
+- No migration.
+- Enum names match user-confirmed canonical option (α): `Start, End, Action, Intermediate`.
+
+## Risks & Mitigation
+
+**Risk 1: a third-party tool reads the DB column directly**
+- *Risk*: external SQL queries comparing to literal strings still work because we kept the lowercase format.
+- *Mitigation*: type handler emits exactly the same lowercase strings.
+
+Full change entry: `_docs/04_refactoring/03-code-quality-refactoring/list-of-changes.md` (C17).