fix(vision): CI has no numpy — the vehicle-stage tests need it without the alpr extra

CI syncs the service with `uv sync --frozen` (no extra), so test_vehicle.py's module-level
numpy import broke collection in ci.yml and both build-images runs. numpy joins the dev
group (the service imports it lazily); the one test that resizes with OpenCV skips when
cv2 is absent. Reproduced locally in a CI-identical env: 13 passed, 1 skipped; ruff + mypy clean.

Claude-Session: https://claude.ai/code/session_01FWncR69HgGPuei1dLrW3cU

apps/vision/pyproject.toml

@@ -35,6 +35,9 @@ dev = [
     "pytest>=8.3",
     "httpx>=0.27",          # FastAPI TestClient transport
     "mypy>=1.13",
+    # The vehicle stage's post-processing tests run on synthetic tensors without the model
+    # stack (CI syncs WITHOUT the alpr extra); the service itself imports numpy lazily.
+    "numpy>=1.26",
 ]
 
 [tool.ruff]