feat: add ImportService for CSV import with duplicate detection

Orchestrates CSV reading, description normalization, and transaction
storage. Uses count-based duplicate detection so legitimate repeated
transactions (same date/amount/description) in a single file are all
imported, while re-importing the same file correctly identifies every
row as a duplicate.

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

tests/services/test_importer.py

@@ -0,0 +1,110 @@
+# tests/services/test_importer.py
+import datetime
+from pathlib import Path
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session
+
+from src.db import Base
+from src.models import *
+from src.seed import seed_categories
+from src.services.importer import ImportService
+
+RAWDATA = Path(__file__).parent.parent.parent / "rawdata"
+
+
+def make_session():
+    engine = create_engine("sqlite:///:memory:")
+    Base.metadata.create_all(engine)
+    return Session(engine)
+
+
+def setup_chase_account(session):
+    member = HouseholdMember(name="Andrew", relationship="self")
+    session.add(member)
+    session.flush()
+    account = Account(name="Chase Freedom", institution="Chase", account_type="credit", owner_id=member.id)
+    session.add(account)
+    session.flush()
+    seed_categories(session)
+    return account
+
+
+def setup_checking_account(session):
+    member = HouseholdMember(name="Andrew", relationship="self")
+    session.add(member)
+    session.flush()
+    account = Account(name="WF Checking", institution="Wells Fargo", account_type="checking", owner_id=member.id, is_shared=True)
+    session.add(account)
+    session.flush()
+    seed_categories(session)
+    return account
+
+
+def test_import_chase_csv():
+    session = make_session()
+    account = setup_chase_account(session)
+    column_map = {
+        "date": "Transaction Date",
+        "amount": "Amount",
+        "description": "Description",
+        "source_category": "Category",
+    }
+    svc = ImportService(session)
+    result = svc.import_csv(
+        RAWDATA / "Chase0372_Activity20260101_20260210_20260210.CSV",
+        account_id=account.id,
+        column_map=column_map,
+        amount_logic="signed",
+    )
+    assert result["imported"] > 0
+    assert result["duplicates"] == 0
+    txns = session.query(Transaction).all()
+    assert len(txns) == result["imported"]
+    sephora = [t for t in txns if "SEPHORA" in t.description]
+    assert len(sephora) == 1
+    assert float(sephora[0].amount) == -75.00
+
+
+def test_import_checking_csv():
+    session = make_session()
+    account = setup_checking_account(session)
+    column_map = {
+        "date": 0,
+        "amount": 1,
+        "description": 4,
+    }
+    svc = ImportService(session)
+    result = svc.import_csv(
+        RAWDATA / "Checking1.csv",
+        account_id=account.id,
+        column_map=column_map,
+        amount_logic="signed",
+    )
+    assert result["imported"] > 0
+    txns = session.query(Transaction).all()
+    assert len(txns) > 50
+
+
+def test_duplicate_detection():
+    session = make_session()
+    account = setup_chase_account(session)
+    column_map = {
+        "date": "Transaction Date",
+        "amount": "Amount",
+        "description": "Description",
+    }
+    svc = ImportService(session)
+    result1 = svc.import_csv(
+        RAWDATA / "Chase0372_Activity20260101_20260210_20260210.CSV",
+        account_id=account.id,
+        column_map=column_map,
+        amount_logic="signed",
+    )
+    result2 = svc.import_csv(
+        RAWDATA / "Chase0372_Activity20260101_20260210_20260210.CSV",
+        account_id=account.id,
+        column_map=column_map,
+        amount_logic="signed",
+    )
+    assert result2["duplicates"] == result1["imported"]
+    assert result2["imported"] == 0