feat(sources): контракт источников, worker и синк ZenMoney + ЦБ

Source.sync(ctx) -> SyncResult пишет только raw_* и возвращает курсор; локи,
журнал, ошибки и продвижение курсора берёт на себя worker/runner.

ZenMoney читается единственным доступным способом — POST /v8/diff/ по
serverTimestamp; токен живёт сутки, поэтому worker ротирует refresh_token через
source_credential. Маппер всегда пересобирает core из полных raw_*, так что
удаление в ZenMoney исчезает и у нас.

ЦБ ходит мимо прокси (trust_env=False) и отдаёт cp1251 с делением на Nominal.
Курсы только по рабочим дням — протяжку по календарю делает аналитика.

Планировщик — APScheduler в отдельном процессе, на источник advisory-лок
sync:<name>, чтобы ручной запуск не пересёкся с плановым.

backend/tests/test_sync.py

@@ -0,0 +1,115 @@
+import pytest
+
+from fintracker.sources import registry
+from fintracker.sources.base import SyncContext, SyncResult
+
+
+class FakeSource:
+    name = "fake"
+
+    def __init__(self) -> None:
+        self.calls = 0
+
+    async def sync(self, ctx: SyncContext) -> SyncResult:
+        self.calls += 1
+        before = int(ctx.cursor_before or 0)
+        return SyncResult(cursor_after=str(before + 1), counts={"rows": 3})
+
+
+class FailingSource:
+    name = "boom"
+
+    async def sync(self, ctx: SyncContext) -> SyncResult:
+        raise RuntimeError("upstream down")
+
+
+@pytest.fixture
+def fake_source():
+    src = registry.register(FakeSource())
+    registry.register(FailingSource())
+    yield src
+    registry.unregister("fake")
+    registry.unregister("boom")
+
+
+async def test_trigger_dedupes_queued_jobs(client, auth_headers, fake_source):
+    r1 = await client.post("/api/v1/sync/fake", headers=auth_headers)
+    r2 = await client.post("/api/v1/sync/fake", headers=auth_headers)
+    assert r1.status_code == 202 and r2.status_code == 202
+    assert r1.json()["id"] == r2.json()["id"]
+
+    r = await client.post("/api/v1/sync/unknown", headers=auth_headers)
+    assert r.status_code == 404
+
+    status = await client.get("/api/v1/sync/status", headers=auth_headers)
+    assert status.status_code == 200
+    by_name = {s["source"]: s for s in status.json()}
+    assert by_name["fake"]["queued"] is True
+    assert by_name["fake"]["cursor"] is None
+
+
+async def test_worker_runs_queued_job_and_advances_cursor(client, auth_headers, fake_source):
+    from fintracker.worker.scheduler import _process_queued_jobs
+
+    await client.post("/api/v1/sync/fake", headers=auth_headers)
+    await _process_queued_jobs()
+    assert fake_source.calls == 1
+
+    status = await client.get("/api/v1/sync/status", headers=auth_headers)
+    fake = next(s for s in status.json() if s["source"] == "fake")
+    assert fake["cursor"] == "1"
+    assert fake["queued"] is False
+    assert fake["last_run_status"] == "ok"
+
+    runs = await client.get("/api/v1/sync/runs", params={"source": "fake"}, headers=auth_headers)
+    assert runs.json()[0]["counts"] == {"rows": 3}
+    assert runs.json()[0]["triggered_by"] == "manual"
+
+
+async def test_failed_sync_is_recorded_not_raised(client, auth_headers, fake_source):
+    from fintracker.worker.runner import run_source
+
+    run = await run_source("boom", triggered_by="cli")
+    assert run.status.value == "error"
+    assert run.error is not None and "upstream down" in run.error
+
+    status = await client.get("/api/v1/sync/status", headers=auth_headers)
+    boom = next(s for s in status.json() if s["source"] == "boom")
+    assert boom["last_run_status"] == "error"
+    assert boom["last_success_at"] is None
+
+
+async def test_metrics_failure_after_a_sync_marks_the_run_as_error(app, fake_source):
+    """The download succeeded, so the cursor stays advanced; the run is still an error,
+    because the metrics the UI reads are stale."""
+    from fintracker.db import get_sessionmaker
+    from fintracker.metrics import refresh as refresh_module
+    from fintracker.models import SyncState
+    from fintracker.worker.runner import run_source
+
+    async def failing_step(session) -> None:
+        raise RuntimeError("step exploded")
+
+    refresh_module.STEPS.append(("test_failing_step", failing_step))
+    try:
+        run = await run_source("fake", triggered_by="cli")
+    finally:
+        refresh_module.STEPS[:] = [s for s in refresh_module.STEPS if s[0] != "test_failing_step"]
+
+    assert run.status.value == "error"
+    assert run.error is not None
+    assert run.error.startswith("metrics refresh failed:")
+    assert "step exploded" in run.error
+    # the sync itself succeeded: the cursor must not replay
+    assert run.cursor_after == "1"
+    async with get_sessionmaker()() as session:
+        state = await session.get(SyncState, "fake")
+        assert state is not None and state.cursor == "1"
+
+
+async def test_a_later_refresh_is_clean_again(app, fake_source):
+    """The temporary failing step is gone, so nothing leaks into other tests."""
+    from fintracker.worker.runner import run_source
+
+    run = await run_source("fake", triggered_by="cli")
+    assert run.status.value == "ok", run.error