[AZ-309] Refactor 02-coupling-refactoring Phase 0-2 artifacts

- Baseline metrics, list of changes, and analysis (research findings,
  refactoring roadmap) for the coupling refactor run
- Six task specs AZ-310..AZ-315 covering endpoint routing through
  ITileService, Services csproj split, consumer rewire, DI extension
  methods, and docs sync
- Existing test coverage assessment for Phase 3 safety net gate
- Dependencies table updated with the refactor block

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

_docs/04_refactoring/02-coupling-refactoring/baseline_metrics.md

@@ -0,0 +1,100 @@
+# Phase 0 — Baseline Metrics (02-coupling-refactoring)
+
+**Date**: 2026-05-10
+**Mode**: Automatic (user-confirmed scope)
+**Goal**: Resolve remaining Medium architecture findings from `architecture_compliance_baseline.md`:
+1. Route the two API endpoints `ServeTile` and `GetTileByLatLon` through `ITileService` (baseline F3).
+2. Split `SatelliteProvider.Services` into per-component csprojs to add a compiler-enforced module boundary (baseline F4).
+
+## Scope and Constraints
+
+- Behavior must be preserved across all changed paths (smoke + unit suite must stay green).
+- No database schema changes.
+- No public HTTP route changes — the same endpoints must accept the same request shapes and return the same response shapes.
+- C# namespaces will change for the moved classes. Tests and `Program.cs` will need their `using` statements updated.
+
+## Current Code Topology
+
+| Project | LOC (.cs, excl. Migrations/bin/obj) | Files |
+|---------|-------------------------------------|-------|
+| SatelliteProvider.Api | 465 | 1 (Program.cs) |
+| SatelliteProvider.Common | 462 | DTOs, interfaces, configs, GeoUtils |
+| SatelliteProvider.DataAccess | 614 | Repositories, Models, Migrations |
+| SatelliteProvider.Services | 2130 | TileService, GoogleMapsDownloaderV2, RegionService + Processing + Queue, RouteService + Processing |
+| SatelliteProvider.Tests | 1070 | xUnit unit tests (35 tests, all passing) |
+| SatelliteProvider.IntegrationTests | 1434 | Console runner, 11 integration scenarios |
+
+`SatelliteProvider.Services` files (proposed split):
+
+| File | Logical Component | Proposed Project |
+|------|-------------------|------------------|
+| TileService.cs | TileDownloader | SatelliteProvider.Services.TileDownloader |
+| GoogleMapsDownloaderV2.cs | TileDownloader | SatelliteProvider.Services.TileDownloader |
+| RegionService.cs | RegionProcessing | SatelliteProvider.Services.RegionProcessing |
+| RegionProcessingService.cs | RegionProcessing | SatelliteProvider.Services.RegionProcessing |
+| RegionRequestQueue.cs | RegionProcessing | SatelliteProvider.Services.RegionProcessing |
+| RouteService.cs | RouteManagement | SatelliteProvider.Services.RouteManagement |
+| RouteProcessingService.cs | RouteManagement | SatelliteProvider.Services.RouteManagement |
+
+## Test Coverage Baseline
+
+| Suite | Count | Status | Source |
+|-------|-------|--------|--------|
+| Unit tests | 35 | All passing | Step 7 run, 2026-05-10 |
+| Integration smoke | 5 scenarios | All passing in 111.86 s | Step 7 run, 2026-05-10 |
+| Integration full | 11 scenarios | Last verified before refactor | full mode preserved behind `--full` flag |
+
+Coverage measurement tooling (Coverlet) is not yet wired into the project. For this refactor, the existing pass rate of unit + smoke is the safety net; we'll re-run both at the end of every phase.
+
+## Code Smell Baseline
+
+From `architecture_compliance_baseline.md`:
+
+| ID | Severity | Status | Action in this run |
+|----|----------|--------|--------------------|
+| F1 | High | Resolved (testability refactor) | None |
+| F2 | High | Resolved (testability refactor) | None |
+| F3 | Medium | Open | **Address in this run** |
+| F4 | Medium | Open | **Address in this run** |
+| F5 | Low | Open | Will be auto-corrected by F4 (module-layout doc rewrite) |
+
+No new architecture findings were added by Step 6 (Implement Tests) or Step 7 (Run Tests).
+
+## Performance Baseline
+
+| Metric | Value | Source |
+|--------|-------|--------|
+| Smoke wall-clock | 111.86 s | Step 7 run |
+| Unit suite wall-clock | ~1.2 s | Docker `dotnet test` |
+| Build time (cold restore + build, all projects) | ~30 s | Docker `dotnet build` |
+
+Targets after refactor: no measurable regression in smoke or unit time. Build time may increase slightly (more csproj boundaries → more restore steps) but should stay <60 s cold.
+
+## Dependencies
+
+No new package dependencies are required for either change. The split moves existing code into new csproj files.
+
+## Functionality Inventory
+
+| Endpoint | Current Coupling Issue | Behavior Preserved? |
+|----------|------------------------|---------------------|
+| GET `/tiles/{z}/{x}/{y}` (`ServeTile`) | injects `ISatelliteDownloader` + `ITileRepository` + `IMemoryCache` | Yes — moves logic into TileService |
+| GET `/api/satellite/tiles/latlon` (`GetTileByLatLon`) | injects `ISatelliteDownloader` + `ITileRepository` | Yes — moves logic into TileService |
+| All other endpoints | Already route through services | Unchanged |
+
+## Self-Verification
+
+- [x] RUN_DIR created (`_docs/04_refactoring/02-coupling-refactoring/`).
+- [x] Metrics measured for the categories that apply (coverage proxy via test count, code smells from baseline doc, performance from Step 7 run, build time from prior runs, deps from csproj files).
+- [x] Functionality inventory complete for the in-scope endpoints.
+- [x] Measurements reproducible: every count above can be recomputed by running `find ... | wc -l`, `dotnet test`, or reading the linked baseline doc.
+
+## Goals (success criteria)
+
+1. After the refactor, `Program.cs` has zero direct injections of `ISatelliteDownloader`, `ITileRepository`, or `IMemoryCache` for tile endpoints — they all flow through `ITileService`.
+2. The seven Services files are physically split into three csprojs (`Services.TileDownloader`, `Services.RegionProcessing`, `Services.RouteManagement`) with explicit `ProjectReference` boundaries.
+3. `SatelliteProvider.Services.csproj` is deleted (or renamed to a meta-package; deletion preferred).
+4. Unit suite: 35/35 still passing.
+5. Integration smoke suite: still passing in <120 s.
+6. `architecture_compliance_baseline.md` (or a refreshed copy) shows F3 and F4 as **Resolved**.
+7. `module-layout.md` is updated to reflect the new project layout (resolves F5 incidentally).