Initial commit: backend API, data models, and test suite

FastAPI backend for personal health and skincare data with MCP export.
Includes SQLModel models for products, inventory, medications, lab results,
routines, and skin condition snapshots. Pytest suite with 111 tests running
on SQLite in-memory (no PostgreSQL required).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/tests/test_inventory.py

@@ -0,0 +1,54 @@
+import uuid
+
+
+def test_get_inventory_by_id(client, created_product):
+    pid = created_product["id"]
+    r = client.post(f"/products/{pid}/inventory", json={"is_opened": False})
+    assert r.status_code == 201
+    inv_id = r.json()["id"]
+
+    r2 = client.get(f"/inventory/{inv_id}")
+    assert r2.status_code == 200
+    assert r2.json()["id"] == inv_id
+
+
+def test_get_inventory_not_found(client):
+    r = client.get(f"/inventory/{uuid.uuid4()}")
+    assert r.status_code == 404
+
+
+def test_update_inventory_opened(client, created_product):
+    pid = created_product["id"]
+    r = client.post(f"/products/{pid}/inventory", json={"is_opened": False})
+    inv_id = r.json()["id"]
+
+    r2 = client.patch(
+        f"/inventory/{inv_id}",
+        json={"is_opened": True, "opened_at": "2026-01-15"},
+    )
+    assert r2.status_code == 200
+    data = r2.json()
+    assert data["is_opened"] is True
+    assert data["opened_at"] == "2026-01-15"
+
+
+def test_update_inventory_not_found(client):
+    r = client.patch(f"/inventory/{uuid.uuid4()}", json={"is_opened": True})
+    assert r.status_code == 404
+
+
+def test_delete_inventory(client, created_product):
+    pid = created_product["id"]
+    r = client.post(f"/products/{pid}/inventory", json={})
+    inv_id = r.json()["id"]
+
+    r2 = client.delete(f"/inventory/{inv_id}")
+    assert r2.status_code == 204
+
+    r3 = client.get(f"/inventory/{inv_id}")
+    assert r3.status_code == 404
+
+
+def test_delete_inventory_not_found(client):
+    r = client.delete(f"/inventory/{uuid.uuid4()}")
+    assert r.status_code == 404