[AZ-315] Sync architecture docs after coupling refactor

Phase C of architecture coupling refactor (epic AZ-309). Closes the
last baseline finding (F5 — DataAccess incorrectly documented as
importing Common) and synchronizes the rest of _docs/02_document/
with the post-split project layout from AZ-312/313/314:

- module-layout.md: per-component sections for the three new csprojs
  with explicit ProjectReferences and the no-cross-sibling-reference
  invariant the split enforces.
- architecture.md: components and internal-communication tables
  updated to show calls flow through Common interfaces.
- architecture_compliance_baseline.md: F1..F5 marked Resolved with
  task IDs and commit refs; baseline summary now 0 findings.
- diagrams/components.md, components/03_tile_downloader/description.md,
  modules/{common_interfaces,services_tile_service,
  services_google_maps_downloader,tests_unit}.md updated for the
  split, RateLimitException relocation, and new ITileService methods.

Documentation-only batch — no code, no tests, no build changes.
Epic AZ-309 complete (6 tasks across 3 batches).

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

_docs/02_document/modules/services_tile_service.md

@@ -1,29 +1,35 @@
 # Module: Services/TileService
 
 ## Purpose
-Orchestrates tile downloading and persistence. Bridges the downloader (Google Maps) with the tile repository (PostgreSQL), handling cache checks, entity creation, and metadata mapping.
+Orchestrates tile downloading and persistence. Bridges the downloader (Google Maps) with the tile repository (PostgreSQL), handling in-memory caching, entity creation, and metadata mapping. Single ownership point for all tile read/write business logic — both region-batch and single-tile API endpoints route through this service.
+
+**csproj**: `SatelliteProvider.Services.TileDownloader/TileService.cs`
 
 ## Public Interface
 
 ### TileService (implements ITileService)
 - `DownloadAndStoreTilesAsync(double lat, double lon, double sizeMeters, int zoomLevel, CancellationToken) → Task<List<TileMetadata>>`:
   1. Queries existing tiles in the region from the repository (filtered to current year's version)
-  2. Calls `GoogleMapsDownloaderV2.GetTilesWithMetadataAsync` with existing tiles to skip
+  2. Calls `ISatelliteDownloader.GetTilesWithMetadataAsync` with existing tiles to skip
   3. Creates `TileEntity` for each newly downloaded tile and inserts via repository (upsert)
   4. Returns combined list of existing + new tile metadata
 - `GetTileAsync(Guid id) → Task<TileMetadata?>`: single tile lookup
 - `GetTilesByRegionAsync(double lat, double lon, double sizeMeters, int zoomLevel) → Task<IEnumerable<TileMetadata>>`: query tiles in a region
+- `GetOrDownloadTileAsync(int z, int x, int y, CancellationToken) → Task<TileBytes>` (AZ-310): cache → repository → downloader fallback for single Z/X/Y serving
+- `DownloadAndStoreSingleTileAsync(double latitude, double longitude, int zoomLevel, CancellationToken) → Task<TileMetadata>` (AZ-311): download one tile by lat/lon, persist, return metadata
 
 ## Internal Logic
 - Version is `DateTime.UtcNow.Year` — tiles are considered fresh for the current calendar year
 - `MapToMetadata(TileEntity) → TileMetadata`: entity-to-DTO mapping (static helper)
 - Tile size hardcoded to 256 pixels, image type "jpg"
 - `MapsVersion` formatted as `"downloaded_{date}"`
+- `IMemoryCache` keyed by `(z, x, y)` with 1h absolute / 30min sliding expiration; populated on first hit and on downloader fallback
 
 ## Dependencies
-- `GoogleMapsDownloaderV2` (concrete class, not interface)
+- `ISatelliteDownloader` (resolved via DI; concrete is `GoogleMapsDownloaderV2`)
 - `ITileRepository`
-- `SatelliteProvider.Common.DTO` — GeoPoint, TileMetadata
+- `IMemoryCache` (registered by `AddTileDownloader()`)
+- `SatelliteProvider.Common.DTO` — GeoPoint, TileMetadata, TileBytes
 - `SatelliteProvider.DataAccess.Models` — TileEntity
 
 ## Consumers