[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/common_configs.md

@@ -0,0 +1,63 @@
+# Module: Common/Configs
+
+## Purpose
+Configuration POCOs that bind to `appsettings.json` sections via `IOptions<T>` pattern.
+
+## Public Interface
+
+### MapConfig
+- `Service` (string): map provider name (e.g., "GoogleMaps")
+- `ApiKey` (string): API key for the map provider
+
+### StorageConfig
+- `TilesDirectory` (string): base path for tile storage (default: `/tiles`)
+- `ReadyDirectory` (string): base path for output files (default: `/ready`)
+- `GetTileSubdirectoryPath(int zoomLevel, int tileX, int tileY) → string`: computes bucketed subdirectory path (`{tiles}/{zoom}/{xBucket}/{yBucket}`) using integer division by 1000
+- `GetTileFilePath(int zoomLevel, int tileX, int tileY, string timestamp) → string`: computes full file path with timestamped filename (`tile_{z}_{x}_{y}_{ts}.jpg`)
+
+### ProcessingConfig
+- `MaxConcurrentDownloads` (int, default: 4): semaphore limit for parallel tile downloads
+- `MaxConcurrentRegions` (int, default: 3): parallel region processing workers
+- `DefaultZoomLevel` (int, default: 20): fallback zoom level
+- `QueueCapacity` (int, default: 100): bounded channel capacity for region request queue
+- `DelayBetweenRequestsMs` (int, default: 50): throttle delay between Google Maps requests
+- `SessionTokenReuseCount` (int, default: 100): tiles per session token before rotation
+
+### DatabaseConfig
+- `ConnectionString` (string): DB connection string (unused — connection string is resolved directly from `IConfiguration` in `Program.cs`)
+
+## Internal Logic
+`StorageConfig.GetTileSubdirectoryPath` buckets tiles by dividing X/Y coordinates by 1000, preventing filesystem performance degradation from too many files in one directory.
+
+## Dependencies
+None (pure POCOs, no internal imports).
+
+## Consumers
+- `Program.cs` — binds from config sections via `builder.Services.Configure<T>()`
+- `GoogleMapsDownloaderV2` — reads `MapConfig`, `StorageConfig`, `ProcessingConfig` via `IOptions<T>`
+- `RegionService` — reads `StorageConfig`
+- `RegionProcessingService` — reads `ProcessingConfig`
+- `RouteProcessingService` — reads `StorageConfig`
+- `RegionRequestQueue` — receives `QueueCapacity` as constructor param
+
+## Data Models
+No domain entities; these are configuration DTOs.
+
+## Configuration
+These classes **define** the configuration shape consumed by all services.
+
+| Config Class | appsettings Section |
+|-------------|-------------------|
+| MapConfig | `MapConfig` |
+| StorageConfig | `StorageConfig` |
+| ProcessingConfig | `ProcessingConfig` |
+| DatabaseConfig | (not wired — connection string read directly) |
+
+## External Integrations
+None.
+
+## Security
+`MapConfig.ApiKey` holds the Google Maps API key. In production, injected via environment variable `MapConfig__ApiKey`.
+
+## Tests
+No dedicated tests.