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/ticker.py

@@ -14,6 +14,13 @@ class Ticker(Base):
     # Company name (e.g. "Biogen Inc."); backfilled from Alpaca, nullable for
     # symbols Alpaca doesn't know.
     name: Mapped[str | None] = mapped_column(String(120), nullable=True)
+    # SEC issuer identity, refreshed by the SEC fundamentals import from
+    # company_tickers.json / submissions. The only ticker<->issuer join point;
+    # multi-class tickers (GOOG/GOOGL) share these values. Nullable: not every
+    # symbol resolves to a CIK (e.g. ADRs, foreign issuers not in SEC data).
+    cik: Mapped[str | None] = mapped_column(String(10), nullable=True)
+    sic: Mapped[str | None] = mapped_column(String(4), nullable=True)
+    sic_description: Mapped[str | None] = mapped_column(String(160), nullable=True)
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), default=datetime.utcnow, nullable=False
     )
@@ -28,3 +35,4 @@ class Ticker(Base):
     trade_setups = relationship("TradeSetup", back_populates="ticker", cascade="all, delete-orphan")
     watchlist_entries = relationship("WatchlistEntry", back_populates="ticker", cascade="all, delete-orphan")
     ingestion_progress = relationship("IngestionProgress", back_populates="ticker", cascade="all, delete-orphan", uselist=False)
+    earnings_events = relationship("EarningsEvent", back_populates="ticker", cascade="all, delete-orphan")