feat(dolt): migration 026 + models — fundamentals/earnings schema (A1 schema)

First reviewable slice of workstream A: schema only, no importers, no data.

- data_import_runs: lean batch-import audit (source/revision/status,
  row_counts_json + validation_json as Text-holding-JSON per repo convention).
- fundamental_snapshots: CIK-keyed, one immutable row per accession; stores
  per-period raw facts (duration = cumulative YTD/FY, balance-sheet =
  period-end) plus period_start/period_end/fiscal_year/fiscal_period so
  discrete quarters, Q4, TTM and YoY are derived at read time.
- earnings_events: Dolt-sourced calendar + surprise history, unique
  (ticker_id, announce_date).
- tickers: nullable cik/sic/sic_description — the ticker<->issuer join point.

fundamental_data is left untouched (cutover gated separately at A5). Models
registered in app/models/__init__.py; Ticker gains an earnings_events
relationship. Verified: create_all builds the tables, mappers configure, and
migration 026 renders valid Postgres DDL up and down.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/models/data_import_run.py

@@ -0,0 +1,42 @@
+from datetime import date, datetime
+
+from sqlalchemy import Date, DateTime, Index, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+class DataImportRun(Base):
+    """One row per bulk-import attempt (SEC facts / Dolt earnings / Dolt stocks).
+
+    Lean audit record for the batch import framework: every attempt is logged,
+    whether it promoted, was a ``no_op`` (unchanged revision), or ``failed``.
+    ``row_counts`` and ``validation`` hold JSON strings (repo convention — see
+    ``fundamental_data.unavailable_fields_json``), not JSONB; the validation
+    blob carries reconciliation/discrepancy summaries so no separate conflicts
+    table is needed. One run per source at a time is enforced at write time by a
+    Postgres advisory lock keyed by ``source``.
+    """
+
+    __tablename__ = "data_import_runs"
+    __table_args__ = (
+        Index("ix_data_import_runs_source_started", "source", "started_at"),
+    )
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    # sec_facts | dolt_earnings | dolt_stocks
+    source: Mapped[str] = mapped_column(String(32), nullable=False)
+    # Dolt commit hash, or SEC archive SHA-256. Null until known.
+    revision: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    # running | validated | promoted | no_op | failed
+    status: Mapped[str] = mapped_column(String(16), nullable=False)
+    source_max_date: Mapped[date | None] = mapped_column(Date, nullable=True)
+    row_counts_json: Mapped[str | None] = mapped_column(Text, nullable=True)
+    validation_json: Mapped[str | None] = mapped_column(Text, nullable=True)
+    started_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=datetime.utcnow, nullable=False
+    )
+    completed_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    error_details: Mapped[str | None] = mapped_column(Text, nullable=True)