Implement FIN-WP-0001-T06 HTTP runway read surface

Add create_runway_router() following the hub-core factory pattern,
expose GET /runway/summary and /runway/monthly-burn via create_app,
and add finhub serve for local operation.

tests/test_api.py

@@ -0,0 +1,58 @@
+from pathlib import Path
+
+from fastapi.testclient import TestClient
+
+from fin_hub.app import create_app
+from fin_hub.routers.runway import create_runway_router
+from fin_hub.services.evidence import seed_fixture_ledger
+
+
+def _client_for_ledger(ledger: Path) -> TestClient:
+    app = create_app()
+    app.include_router(
+        create_runway_router(ledger_path_resolver=lambda _: ledger),
+        prefix="/test",
+    )
+    return TestClient(app)
+
+
+def test_runway_summary_and_monthly_burn_endpoints(tmp_path: Path):
+    ledger = tmp_path / "ledger.db"
+    seed_fixture_ledger(ledger_path=ledger, opening_balance=12000.0)
+    client = _client_for_ledger(ledger)
+
+    burn_response = client.get("/test/runway/monthly-burn")
+    assert burn_response.status_code == 200
+    burns = burn_response.json()
+    assert any(row["currency"] == "EUR" and row["period_month"] == "2026-06" for row in burns)
+
+    summary_response = client.get("/test/runway/summary")
+    assert summary_response.status_code == 200
+    summary = summary_response.json()
+    assert summary["opening_balance"] == 12000.0
+    assert summary["runway"]["currency"] == "EUR"
+    assert summary["runway"]["monthly_burn"] > 0
+
+
+def test_runway_summary_requires_balance_when_unset(tmp_path: Path):
+    from fin_hub.services.ledger import monthly_summary
+
+    ledger = tmp_path / "empty.db"
+    monthly_summary(ledger_path=ledger)
+    client = _client_for_ledger(ledger)
+    response = client.get("/test/runway/summary")
+    assert response.status_code == 422
+
+
+def test_runway_summary_404_when_ledger_missing(tmp_path: Path):
+    ledger = tmp_path / "missing.db"
+    client = _client_for_ledger(ledger)
+    response = client.get("/test/runway/summary?balance=12000")
+    assert response.status_code == 404
+
+
+def test_create_app_healthz():
+    client = TestClient(create_app())
+    response = client.get("/healthz")
+    assert response.status_code == 200
+    assert response.json()["service"] == "fin-hub"