feat(ledger): импорт отчётов в леджер — приём, дедупликация, pending_instrument

Поток: upload -> raw_report_file (sha256 UNIQUE) -> parse -> raw_report_line,
событий в леджере ещё нет -> preview -> POST /imports/{id}/commit ->
ledger/ingest.py резолвит инструмент, считает dedupe_key, пишет event
confirmed | shadow (plan §1.6 B) — сравнивая account.primary_event_source
с источником отчёта, а не гадая. Нерезолвленный инструмент ждёт в
pending_instrument, никогда не угадывается; POST /instruments/pending/{id}/resolve
привязывает и пересобирает лоты.

ledger/dedupe.py — shadow-матчинг случая B двумя проходами (точная дата, затем
±1 рабочий день, жадно 1:1, |price| ±0,5 %). Шаги shadow_dedupe и
report_reconcile зарегистрированы перед quality: оба говорят через FINDINGS.

/instruments/pending регистрируется в app.py ДО routers/instruments.py:
FastAPI сопоставляет маршруты по порядку, и /instruments/{id} с типом int
отвечает 422 на нечисловой сегмент, а не проваливается дальше.

Контракт — docs/ai/import-contract.md, общий для бэкенда и Flutter.

backend/src/fintracker/api/schemas/imports.py

@@ -0,0 +1,200 @@
+"""Schemas for `/imports` and `/instruments/pending`, per `docs/ai/import-contract.md`.
+
+Two conventions the Flutter client depends on, both repeated from AGENTS.md because breaking
+either one breaks the generated Dart rather than a test:
+
+* money and quantities are `Money` / `MoneyOpt` — `Decimal` in Python, a string on the wire;
+* every stable key (`broker`, `parse_status`, `kind`, `status`, `asset_class`) is a plain
+  `str`, never an enum. `AssetClass.index` cannot exist as a Dart enum member (it collides
+  with `Enum.index`) and one enum leaking out stops the whole client from compiling.
+"""
+
+from __future__ import annotations
+
+from datetime import date, datetime
+from typing import Literal
+
+from pydantic import BaseModel, Field
+
+from fintracker.api.schemas.common import Money, MoneyOpt
+
+
+class AccountSuggestion(BaseModel):
+    """A broker account the user may attach an import to when the report's number matched none."""
+
+    id: int
+    name: str
+    broker: str | None
+    """tinvest | sber | vtb | other"""
+    source_id: str
+
+
+class ImportCounts(BaseModel):
+    lines: int
+    events_total: int
+    events_new: int
+    """No `event` carries this row's `dedupe_key` yet."""
+    events_duplicate: int
+    """The key is already in the ledger: committing upserts, it does not insert."""
+    events_shadow: int
+    """Rows that will land as `shadow` — this feed is not the account's primary source."""
+    events_pending: int
+    """Rows whose instrument nobody recognises yet."""
+    by_kind: dict[str, int]
+
+
+class PendingInstrumentOut(BaseModel):
+    id: int
+    source: str
+    source_key: str
+    isin: str | None = None
+    ticker: str | None = None
+    board: str | None = None
+    name: str | None = None
+    currency: str | None = None
+    asset_class_hint: str | None = None
+    """share | bond | etf | fund | currency — the report's own wording, never applied alone."""
+    occurrences: int
+    sample_quantity: MoneyOpt = None
+    sample_price: MoneyOpt = None
+    status: str
+    """pending | resolved | ignored"""
+    instrument_id: int | None = None
+    first_seen_file_id: int | None = None
+    created_at: datetime | None = None
+
+
+class ReconciliationPosition(BaseModel):
+    instrument_id: int | None
+    instrument_name: str
+    ticker: str | None
+    isin: str | None
+    qty_report: Money
+    qty_derived: MoneyOpt
+    """Null when the account is unknown or its lots were never rebuilt — never a zero."""
+    qty_delta: MoneyOpt
+    matches: bool
+
+
+class ReconciliationCash(BaseModel):
+    currency: str
+    balance_report: Money
+    balance_derived: MoneyOpt
+    delta: MoneyOpt
+    matches: bool
+
+
+class ReconciliationOut(BaseModel):
+    as_of: date | None
+    positions: list[ReconciliationPosition] = Field(default_factory=list)
+    cash: list[ReconciliationCash] = Field(default_factory=list)
+    matches: bool = True
+
+
+class SampleEventOut(BaseModel):
+    line_no: int
+    kind: str
+    """buy | sell | dividend | coupon | … — the `EventKind` value as a string."""
+    trade_date: date
+    settle_date: date | None = None
+    instrument_key: str | None = None
+    instrument_name: str | None = None
+    instrument_id: int | None = None
+    quantity: MoneyOpt = None
+    price: MoneyOpt = None
+    amount: Money
+    currency: str
+    fee: MoneyOpt = None
+    trade_no: str | None = None
+    dedupe_key: str
+    is_duplicate: bool
+    description: str | None = None
+
+
+class ImportSummary(BaseModel):
+    """One import without the heavy parts — what `GET /imports` lists."""
+
+    id: int
+    broker: str
+    """sber | vtb | csv"""
+    filename: str
+    sha256: str
+    size_bytes: int
+    parser_name: str | None = None
+    parser_version: str | None = None
+    parse_status: str
+    """uploaded | parsed | committed | failed"""
+    error: str | None = None
+    duplicate_of_id: int | None = None
+    """Not null ⇒ these bytes were already uploaded, and this is that import."""
+    account_external_id: str | None = None
+    account_id: int | None = None
+    """Null ⇒ the account is unknown and commit is refused."""
+    account_name: str | None = None
+    period_from: date | None = None
+    period_to: date | None = None
+    uploaded_at: datetime | None = None
+    committed_at: datetime | None = None
+    counts: ImportCounts
+
+
+class ImportPreview(ImportSummary):
+    """The full preview: `POST /imports` and `GET /imports/{id}` both return this."""
+
+    account_suggestions: list[AccountSuggestion] = Field(default_factory=list)
+    pending_instruments: list[PendingInstrumentOut] = Field(default_factory=list)
+    reconciliation: ReconciliationOut
+    warnings: list[str] = Field(default_factory=list)
+    sample_events: list[SampleEventOut] = Field(default_factory=list)
+
+
+class CommitRequest(BaseModel):
+    account_id: int | None = None
+    """Needed only when the preview could not work the account out on its own."""
+    confirm_duplicates: bool = False
+    dry_run: bool = False
+
+
+class ImportResult(BaseModel):
+    import_id: int
+    committed: bool
+    events_created: int
+    events_updated: int
+    events_skipped: int
+    """Rows still waiting on a `pending_instrument`."""
+    events_shadow: int
+    pending_instruments: int
+    reconciliation: ReconciliationOut
+    metrics_refreshed: bool
+
+
+class NewInstrument(BaseModel):
+    """The instrument to create from a report's own data (`action = "create"`)."""
+
+    asset_class: str
+    """share | bond | etf | fund | currency | index | deposit | real_estate | crypto | custom"""
+    name: str
+    currency: str = "RUB"
+    isin: str | None = None
+    ticker: str | None = None
+    board: str | None = None
+    lot: int = 1
+
+
+class PendingResolveRequest(BaseModel):
+    action: Literal["link", "create", "ignore"]
+    instrument_id: int | None = None
+    """Required for `link`."""
+    instrument: NewInstrument | None = None
+    """Required for `create`."""
+
+
+class PendingResolveResult(BaseModel):
+    id: int
+    status: str
+    """resolved | ignored"""
+    instrument_id: int | None = None
+    events_bound: int
+    """How many events left `pending` for `confirmed`/`shadow`."""
+    alias_created: bool
+    metrics_refreshed: bool