M4: ingestion management (incremental, GS1 supplement, dedup/conflict, quality, scheduler)

- OFF incremental fetch via search API + persistent watermark (ingest_state, migration 0004)
- GS1 barcode supplement adapter (offline mapping + GS1-style API) filling only gaps with field-level provenance
- Non-GTIN dedup with canonical selection + merge_log; field-level conflict resolution (source trust > recency)
- Quality scoring (0.4 completeness + 0.3 source trust + 0.2 multi-source + 0.1 freshness) wired into load/merge
- Jobs: update_off, dedup, schedule; docs/ingestion-management.md
- 19 new tests (pure + DB-integration), ruff clean

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

ingestion/tests/test_gs1.py

@@ -0,0 +1,53 @@
+from pathlib import Path
+
+from opengoods.adapters.gs1 import GS1Adapter
+from opengoods.etl.supplement import apply_supplement, ensure_gs1_source
+
+MAPPING = Path(__file__).parent / "fixtures" / "gs1_mapping.json"
+GTIN = "06901234567892"
+
+
+def test_gs1_adapter_offline_lookup():
+    adapter = GS1Adapter.from_file(MAPPING)
+    rec = adapter.fetch_barcode(GTIN)
+    assert rec["brand"] == "示例品牌"
+    assert rec["net_content_value"] == 550
+    assert rec["net_content_unit"] == "ml"
+    # An entry that only has empty values yields no supplement.
+    assert adapter.fetch_barcode("00000000000000") is None
+    # Unknown barcode -> None.
+    assert adapter.fetch_barcode("99999999999999") is None
+
+
+def test_gs1_supplement_fills_only_gaps(db_conn):
+    pid = db_conn.execute(
+        "INSERT INTO product (gtin, name) VALUES (%s, %s) RETURNING id", (GTIN, "水")
+    ).fetchone()[0]
+
+    adapter = GS1Adapter.from_file(MAPPING)
+    rec = adapter.fetch_barcode(GTIN)
+    source_id = ensure_gs1_source(db_conn)
+
+    filled = apply_supplement(db_conn, rec, source_id)
+    assert {"brand", "country_of_origin", "net_content"} <= set(filled)
+
+    brand_id, country, net_value, net_unit = db_conn.execute(
+        """
+        SELECT brand_id, country_of_origin, net_content_value, net_content_unit
+        FROM product WHERE id = %s
+        """,
+        (pid,),
+    ).fetchone()
+    assert brand_id is not None
+    assert country == "China"
+    assert float(net_value) == 550.0
+    assert net_unit == "ml"
+
+    fields = db_conn.execute(
+        "SELECT fields FROM product_source WHERE product_id = %s AND source_id = %s",
+        (pid, source_id),
+    ).fetchone()[0]
+    assert "brand" in fields
+
+    # Re-applying does nothing because the gaps are now filled.
+    assert apply_supplement(db_conn, rec, source_id) == []