Implement FIN-WP-0001 ledger, evaluate, and evidence lane (T03–T05)

Add SQLite-backed cost ledger with import/summary CLI, cron-friendly
evaluate command with federation emit, and dogfood evidence artefact
generation from fixture CSVs.

tests/test_ledger.py

@@ -0,0 +1,60 @@
+from pathlib import Path
+
+import pytest
+
+from fin_hub.services.evaluate import evaluate_runway
+from fin_hub.services.evidence import build_runway_report, seed_fixture_ledger, write_runway_evidence
+from fin_hub.services.ledger import import_csv, monthly_burn_series, monthly_summary, set_opening_balance
+
+FIXTURES = Path(__file__).parent / "fixtures"
+
+
+def test_ledger_import_and_monthly_summary(tmp_path: Path):
+    ledger = tmp_path / "ledger.db"
+    set_opening_balance(ledger, 12000.0)
+
+    cloud = import_csv(FIXTURES / "cloud-costs.csv", "cloud", ledger_path=ledger)
+    host = import_csv(FIXTURES / "hosteurope.csv", "hosteurope", ledger_path=ledger)
+
+    assert cloud.rows_imported == 3
+    assert host.rows_imported == 2
+
+    rollups = monthly_summary(ledger_path=ledger)
+    eur_totals = {rollup.period_month: rollup.total for rollup in rollups if rollup.currency == "EUR"}
+    assert eur_totals["2026-06"] == pytest.approx(85.5 + 99.8)
+
+    burns = monthly_burn_series(ledger_path=ledger, currency="EUR")
+    assert burns == [pytest.approx(185.3)]
+
+
+def test_ledger_import_skips_unchanged_file(tmp_path: Path):
+    ledger = tmp_path / "ledger.db"
+    first = import_csv(FIXTURES / "cloud-costs.csv", "cloud", ledger_path=ledger)
+    second = import_csv(FIXTURES / "cloud-costs.csv", "cloud", ledger_path=ledger)
+    assert first.rows_imported == 3
+    assert second.skipped is True
+    assert second.rows_imported == 0
+
+
+def test_evaluate_runway_from_ledger(tmp_path: Path):
+    ledger = tmp_path / "ledger.db"
+    seed_fixture_ledger(ledger_path=ledger, opening_balance=12000.0)
+    report = evaluate_runway(ledger_path=ledger, alert_threshold_months=3.0)
+    assert report["runway"]["current_balance"] == 12000.0
+    assert report["runway"]["monthly_burn"] > 0
+
+
+def test_build_runway_report_and_write_evidence(tmp_path: Path):
+    ledger = tmp_path / "ledger.db"
+    seed_fixture_ledger(ledger_path=ledger, opening_balance=12000.0)
+    text = build_runway_report(ledger_path=ledger)
+    assert "Runway Dogfood Evidence" in text
+    assert "2026-06" in text
+
+    output = write_runway_evidence(
+        ledger_path=ledger,
+        output_dir=tmp_path / "evidence",
+        opening_balance=12000.0,
+    )
+    assert output.exists()
+    assert "runway-dogfood-" in output.name