feat(analytics): метрики фазы 1 — классификация, net worth, потоки, расходы, runway

fx_rate_daily получает строку на каждый календарный день: котировки ЦБ тянутся
вперёд (и назад до первой), is_carried это помечает, RUB = 1.0 всегда. Дальше
любая сумма конвертируется по курсу СВОЕЙ даты, а не сегодняшнему.

Net worth восстанавливается назад от текущего account.balance по транзакциям —
ZenMoney отдаёт остаток, а не историю; поэтому сегодняшняя строка совпадает с
тем, что показывает ZenMoney, а каждая прошлая с ней согласована.

Нет курса — не подстановка, а NULL и строка в metric_data_quality. Туда же
попадает то, что шаги заметили по дороге: правило без совпадений, счёт без
баланса, перевод через границу net worth.

backend/src/fintracker/analytics/__init__.py

@@ -0,0 +1,137 @@
+"""Phase-1 analytics: rebuild every `metric_*` table from core data (plan §3).
+
+The steps are registered on `metrics.refresh.STEPS` in the order they must run:
+
+    fx -> classify -> networth -> cashflow -> spending -> runway -> quality
+
+Registration happens lazily from `refresh_all` (see `register_steps`) so importing
+`fintracker.metrics.refresh` stays free of the analytics import graph.
+
+`FINDINGS` is the in-memory collector the steps use to report data-quality problems they
+notice in passing (an unknown category in a rule, an account with no balance). It is reset
+by the first step of a refresh and drained by the last one (`quality`).
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from datetime import date, datetime
+from typing import Any
+from zoneinfo import ZoneInfo
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from fintracker.config import get_settings
+
+
+def today_local() -> date:
+    """Today in the deployment timezone (MSK by default) — metrics end on this day."""
+    return datetime.now(ZoneInfo(get_settings().timezone)).date()
+
+
+async def ledger_date_range(session: AsyncSession) -> tuple[date | None, date | None]:
+    """First and last date the ledger actually covers, ignoring deleted transactions.
+
+    Deleted rows are tombstones every metric already filters out, but they still carry a
+    date — and ZenMoney hands out `1970-01-01` for one that was never really dated. Reading
+    the bounds without the filter stretches every date spine built from them (the FX grid,
+    the net-worth series) over five empty decades.
+    """
+    from sqlalchemy import func, select
+
+    from fintracker.models import CashTxn
+
+    row = (
+        await session.execute(
+            select(func.min(CashTxn.date), func.max(CashTxn.date)).where(CashTxn.deleted.is_(False))
+        )
+    ).one()
+    return row[0], row[1]
+
+
+@dataclass(frozen=True)
+class Finding:
+    """One data-quality observation; identical findings are merged by `quality`."""
+
+    check_name: str
+    severity: str
+    """info | warn | error"""
+    detail: str
+    count: int = 1
+    ref: dict[str, Any] | None = None
+
+
+@dataclass
+class FindingCollector:
+    items: list[Finding] = field(default_factory=list)
+
+    def reset(self) -> None:
+        self.items.clear()
+
+    def add(
+        self,
+        check_name: str,
+        severity: str,
+        detail: str,
+        *,
+        count: int = 1,
+        ref: dict[str, Any] | None = None,
+    ) -> None:
+        self.items.append(Finding(check_name, severity, detail, count, ref))
+
+
+FINDINGS = FindingCollector()
+
+_registered = False
+
+
+async def _step_fx(session: AsyncSession) -> None:
+    """First step of every refresh: clear findings from the previous run, then rebuild FX."""
+    from fintracker.pricing.fx import rebuild_fx_daily
+
+    FINDINGS.reset()
+    await rebuild_fx_daily(session)
+
+
+def register_steps() -> None:
+    """Idempotently put the phase-1 steps on the refresh registry, in order."""
+    global _registered
+    if _registered:
+        return
+    _registered = True
+
+    from fintracker.analytics import (
+        cashflow,
+        classify,
+        networth,
+        quality,
+        returns,
+        runway,
+        spending,
+        valuation,
+    )
+    from fintracker.ledger.rebuild import rebuild_lots
+    from fintracker.metrics.refresh import register_step
+
+    register_step("fx", _step_fx)
+    register_step("classify", classify.rebuild_classification)
+    # lots need FX (cost in RUB at the open date) and feed every later valuation step
+    register_step("lots", rebuild_lots)
+    # valuation prices the positions the lots describe; returns reads the series it writes
+    register_step("valuation", valuation.rebuild_valuation)
+    register_step("returns", returns.rebuild_returns)
+    register_step("networth", networth.rebuild_net_worth_daily)
+    register_step("cashflow", cashflow.rebuild_cash_flow_monthly)
+    register_step("spending", spending.rebuild_spending_by_category)
+    register_step("runway", runway.rebuild_runway)
+    register_step("quality", quality.rebuild_data_quality)
+
+
+__all__ = [
+    "FINDINGS",
+    "Finding",
+    "FindingCollector",
+    "ledger_date_range",
+    "register_steps",
+    "today_local",
+]