[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/02_document/modules/tests_unit.md

@@ -0,0 +1,23 @@
+# Module: Tests/SatelliteProvider.Tests
+
+## Purpose
+Unit test project. Currently contains only a single dummy test as a placeholder.
+
+## Public Interface
+
+### DummyTests
+- `Dummy_ShouldWork()`: asserts `1 == 1`
+
+## Internal Logic
+No meaningful test logic.
+
+## Dependencies
+- Project references: `SatelliteProvider.Services`, `SatelliteProvider.Common`
+- NuGet: xUnit (2.5.3), Moq (4.20.72), FluentAssertions (8.8.0), coverlet.collector (6.0.0), Microsoft.NET.Test.Sdk (17.8.0), Microsoft.Extensions.* (Configuration, DI, Logging, Options, Http)
+- Has `appsettings.json` copied to output (empty config for potential future test setups)
+
+## Consumers
+- CI pipeline (`01-test.yml`) runs `dotnet test` against this project
+
+## Tests
+This IS the test module. Coverage: effectively zero (only a dummy test).