chore: decommission FMP, Finnhub and Alpha Vantage (A6)

The A5 cutover has been on and observed in production, so SEC Company Facts +
DoltHub earnings are already the live source for `fundamental_data`. This
removes everything the legacy path still occupied.

Gone: the three providers and their config/env keys; the weekly
`fundamental_collector` job; the cutover toggle (SEC + Dolt is now the
unconditional path, so `off` can no longer silently freeze scoring inputs); the
A5 parity report, whose deltas became structurally zero once the candidate
builder started writing the table it compared against; and the FMP tier of
universe bootstrap.

Two behavioral notes:

- Disabling **SEC Fundamentals Import** now stops the SEC network fetch only.
  The local cache refresh moved outside the job-enable check, because candidates
  also derive from daily closes and earnings events — freezing those on an
  ingestion pause would stale scoring with no fallback left to recover from.
- `/ingestion/fetch?sources=fundamentals` still accepts the key and reports
  `skipped`; there is no per-ticker fetch any more.

Migration 029 does not blanket-delete the leftover settings rows. Migrations run
before the service restart, and pre-A6 code reads an absent `job_*_enabled` row
as *enabled* — so the two behavior-bearing keys become tombstones pinned to safe
values (hidden in Admin) and only the inert three are deleted. Removing the
provider keys from the production `.env` is the matching rollout step.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/unit/test_rr_scanner_preservation.py

@@ -24,7 +24,6 @@ from app.models.ohlcv import OHLCVRecord
 from app.models.paper_trade import PaperTrade
 from app.models.signal_context_snapshot import SignalContextSnapshot
 from app.models.sec_filing_gap import SecFilingGap
-from app.models.settings import SystemSetting
 from app.models.sr_level import SRLevel
 from app.models.ticker import Ticker
 from app.models.trade_setup import TradeSetup
@@ -524,10 +523,6 @@ async def test_get_trade_setups_hides_active_sec_filing_gap(
     db_session.add(ticker)
     await db_session.flush()
     db_session.add_all([
-        SystemSetting(
-            key="fundamental_data_sec_dolt_cutover_enabled",
-            value="true",
-        ),
         SecFilingGap(
             cik=ticker.cik,
             accession="0000000042-26-000001",