refactor(status): introduce OrderStatus enum, replace string literals

Centralized order status values in api/app/constants.py via a
str-valued Enum so comparisons keep working. Replaced literals in:
- services: sync_service, sqlite_service, retry_service
- routers: sync, dashboard
- templates: dashboard.html, logs.html
- static JS: shared (ORDER_STATUS mirror), dashboard, logs
- tests: requirements, order_items_overwrite, business_rules

MALFORMED intentionally NOT added — introduced in follow-up PR2
(per-order failure isolation).

Full test suite: 231 unit + 33 e2e pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/tests/test_order_items_overwrite.py

@@ -35,6 +35,7 @@ if _api_dir not in sys.path:
 
 from app import database
 from app.services import sqlite_service
+from app.constants import OrderStatus
 
 
 @pytest.fixture(autouse=True)
@@ -69,7 +70,7 @@ async def _seed_order(order_number="TEST-001"):
         order_number=order_number,
         order_date="2026-01-01",
         customer_name="Test",
-        status="IMPORTED",
+        status=OrderStatus.IMPORTED.value,
     )
 
 
@@ -192,5 +193,5 @@ async def test_mark_order_deleted_removes_items():
     finally:
         await db.close()
     assert row is not None
-    assert row["status"] == "DELETED_IN_ROA"
+    assert row["status"] == OrderStatus.DELETED_IN_ROA.value
     assert row["id_comanda"] is None