[AZ-284] Autodev baseline + testability refactor

Phase A baseline outputs from /autodev (Steps 1-5):
- Problem & solution docs (_docs/00_problem, _docs/01_solution)
- Codebase documentation (_docs/02_document) incl. architecture,
  module-layout, glossary, system-flows, baseline compliance scan
- Test specs (blackbox, performance, resilience, security, resource,
  traceability matrix)
- Test task decomposition (_docs/02_tasks/todo): AZ-285..AZ-290
- Testability refactor (_docs/04_refactoring/01-testability-refactoring):
  - TC-01 Move DownloadedTileInfoV2 + new ExistingTileInfo to Common.DTO
  - TC-02 Replace dead ISatelliteDownloader API with real signatures
  - TC-03 GoogleMapsDownloaderV2 implements ISatelliteDownloader
  - TC-04 TileService depends on ISatelliteDownloader (mockable)
  - TC-05 DI + endpoints use ISatelliteDownloader
- Test runner scripts (scripts/run-tests.sh, run-performance-tests.sh)
- Autodev state pointer (_docs/_autodev_state.md)

Prepares the codebase for AZ-285..AZ-290 unit/integration test work.

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

_docs/04_refactoring/01-testability-refactoring/list-of-changes.md

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+# Testability Refactoring — List of Changes
+
+Mode: guided
+Source: autodev-testability-analysis + architecture-compliance-baseline F1/F2
+
+## TC-01: Move DownloadedTileInfoV2 to Common
+
+**Files**: `SatelliteProvider.Services/GoogleMapsDownloaderV2.cs` → `SatelliteProvider.Common/DTO/DownloadedTileInfoV2.cs`
+**Problem**: `DownloadedTileInfoV2` is defined in Services alongside the concrete downloader. The interface in Common cannot reference it, blocking the interface fix.
+**Change**: Move the record to `SatelliteProvider.Common.DTO`. Update namespace references in GoogleMapsDownloaderV2 and TileService.
+**Risk**: Low — record has no dependencies on Services-specific types.
+
+## TC-02: Update ISatelliteDownloader interface
+
+**Files**: `SatelliteProvider.Common/Interfaces/ISatelliteDownloader.cs`
+**Problem**: Current interface has a single method `GetTiles` with a signature that doesn't match any usage in the codebase (dead code, per baseline F2).
+**Change**: Replace with the two methods actually needed by callers:
+- `DownloadSingleTileAsync(double latitude, double longitude, int zoomLevel, CancellationToken token = default)`
+- `GetTilesWithMetadataAsync(GeoPoint centerGeoPoint, double radiusM, int zoomLevel, IEnumerable<ExistingTileInfo> existingTiles, CancellationToken token = default)`
+Introduce `ExistingTileInfo` record in Common to avoid referencing DataAccess.TileEntity from the interface.
+**Risk**: Low — the old interface was unused.
+
+## TC-03: GoogleMapsDownloaderV2 implements ISatelliteDownloader
+
+**Files**: `SatelliteProvider.Services/GoogleMapsDownloaderV2.cs`
+**Problem**: Concrete class does not implement the interface, so it cannot be swapped in tests (baseline F1).
+**Change**: Add `: ISatelliteDownloader` to class declaration. Adjust `GetTilesWithMetadataAsync` parameter from `IEnumerable<TileEntity>` to `IEnumerable<ExistingTileInfo>`.
+**Risk**: Medium — method signature change requires updating callers.
+**Dependencies**: TC-01, TC-02
+
+## TC-04: TileService depends on ISatelliteDownloader
+
+**Files**: `SatelliteProvider.Services/TileService.cs`
+**Problem**: Constructor takes `GoogleMapsDownloaderV2` (concrete). Cannot mock in unit tests.
+**Change**: Change constructor parameter and field type from `GoogleMapsDownloaderV2` to `ISatelliteDownloader`. Map `TileEntity` to `ExistingTileInfo` before calling the interface.
+**Risk**: Low — no public API change.
+**Dependencies**: TC-02, TC-03
+
+## TC-05: Update DI registration and API endpoint
+
+**Files**: `SatelliteProvider.Api/Program.cs`
+**Problem**: `GoogleMapsDownloaderV2` registered as concrete singleton. `ServeTile` endpoint injects concrete class directly.
+**Change**: Register as `ISatelliteDownloader` → `GoogleMapsDownloaderV2`. Change `ServeTile` to inject `ISatelliteDownloader`.
+**Risk**: Low — behavior unchanged, just the injection type.
+**Dependencies**: TC-03
+
+## Deferred to Step 8 Refactor
+
+- **Medium finding: ServeTile bypasses service layer** — The endpoint directly uses `ITileRepository` and the downloader instead of `ITileService`. Moving this logic into the service layer would be cleaner but changes module boundaries (not allowed in testability step).
+- **Medium finding: No physical boundaries in Services project** — All services share one project. Splitting into separate projects is a structural change beyond testability scope.

_docs/04_refactoring/01-testability-refactoring/testability_changes_summary.md

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+# Testability Changes Summary
+
+## Applied Changes
+
+### TC-01: Moved DownloadedTileInfoV2 to Common/DTO
+- **Created**: `SatelliteProvider.Common/DTO/DownloadedTileInfoV2.cs`
+- **Created**: `SatelliteProvider.Common/DTO/ExistingTileInfo.cs`
+- **Modified**: `SatelliteProvider.Services/GoogleMapsDownloaderV2.cs` — removed inline record definition, added import
+- **Why**: The return type of the downloader must be accessible from the interface in Common
+
+### TC-02: Updated ISatelliteDownloader interface
+- **Modified**: `SatelliteProvider.Common/Interfaces/ISatelliteDownloader.cs`
+- **Old API**: `Task GetTiles(GeoPoint, double, int, CancellationToken)` — never implemented, dead code
+- **New API**: `DownloadSingleTileAsync(...)` + `GetTilesWithMetadataAsync(...)` — matches actual usage
+- **Why**: Previous interface was dead code; new interface enables mocking the downloader in tests
+
+### TC-03: GoogleMapsDownloaderV2 implements ISatelliteDownloader
+- **Modified**: `SatelliteProvider.Services/GoogleMapsDownloaderV2.cs`
+- **Change**: Class declaration now includes `: ISatelliteDownloader`; `GetTilesWithMetadataAsync` parameter changed from `IEnumerable<TileEntity>` to `IEnumerable<ExistingTileInfo>`
+- **Why**: Concrete class must implement the interface for DI and mocking to work
+
+### TC-04: TileService depends on ISatelliteDownloader
+- **Modified**: `SatelliteProvider.Services/TileService.cs`
+- **Change**: Constructor parameter and field type changed from `GoogleMapsDownloaderV2` to `ISatelliteDownloader`; added mapping from `TileEntity` to `ExistingTileInfo` before calling the interface
+- **Why**: Unit tests can now mock the downloader via the interface
+
+### TC-05: Updated DI registration and API endpoints
+- **Modified**: `SatelliteProvider.Api/Program.cs`
+- **Changes**:
+  - DI: `AddSingleton<GoogleMapsDownloaderV2>()` → `AddSingleton<ISatelliteDownloader, GoogleMapsDownloaderV2>()`
+  - `ServeTile` endpoint: parameter `GoogleMapsDownloaderV2 downloader` → `ISatelliteDownloader downloader`
+  - `GetTileByLatLon` endpoint: parameter `GoogleMapsDownloaderV2 downloader` → `ISatelliteDownloader downloader`
+- **Why**: Endpoints should inject the interface, not the concrete class
+
+## Deferred to Step 8
+
+- ServeTile and GetTileByLatLon endpoints bypass the service layer (inject repository + downloader directly)
+- No physical project boundaries between logical components in the Services project