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>

alembic/versions/029_retire_legacy_fundamentals_settings.py

@@ -0,0 +1,96 @@
+"""Retire the legacy fundamentals settings (A6)
+
+Revision ID: 029
+Revises: 028
+Create Date: 2026-08-07 00:00:00.000000
+
+A6 removed the FMP/Finnhub/Alpha Vantage providers, the weekly
+``fundamental_collector`` job and the A5 parity report. Five SystemSetting rows
+are left over. They are NOT all deleted, because the deploy runs migrations
+before restarting the service: for a short window — and for the whole of any
+rollback — pre-A6 code is still live, and it reads absent rows permissively
+(cutover absent -> disabled; ``job_<name>_enabled`` absent -> enabled). Deleting
+both would hand a rolled-back process a re-armed legacy collector writing over
+the SEC/Dolt cache.
+
+So the two rows that carry behavior become tombstones pinned to the safe value,
+and only the inert ones are deleted. The tombstones are dropped in a later
+release once the rollback window has closed; ``SettingsForm`` hides them
+meanwhile.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = "029"
+down_revision: Union[str, None] = "028"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+# Behavior-bearing under pre-A6 code -> pin to the safe value, keep the row.
+_TOMBSTONES: dict[str, str] = {
+    "fundamental_data_sec_dolt_cutover_enabled": "true",
+    "job_fundamental_collector_enabled": "false",
+}
+
+# Inert either way: an absent cron falls back to a default for a job that no
+# longer registers, and the parity report never wrote anything.
+_OBSOLETE: tuple[str, ...] = (
+    "schedule_fundamentals_cron",
+    "schedule_fundamentals_parity_cron",
+    "job_fundamentals_parity_report_enabled",
+)
+
+_settings = sa.table(
+    "system_settings",
+    sa.column("id", sa.Integer),
+    sa.column("key", sa.String),
+    sa.column("value", sa.Text),
+    sa.column("updated_at", sa.DateTime(timezone=True)),
+)
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+    now = sa.func.now()
+
+    for key, pinned in _TOMBSTONES.items():
+        row = conn.execute(
+            sa.select(_settings.c.value).where(_settings.c.key == key)
+        ).fetchone()
+        old_value = row[0] if row is not None else None
+        print(f"a6_tombstone {key}: {old_value!r} -> {pinned!r}", flush=True)
+        if row is None:
+            conn.execute(
+                sa.insert(_settings).values(key=key, value=pinned, updated_at=now)
+            )
+        elif old_value != pinned:
+            conn.execute(
+                sa.update(_settings)
+                .where(_settings.c.key == key)
+                .values(value=pinned, updated_at=now)
+            )
+
+    # Print the value before deleting — a bare DELETE cannot be undone from the
+    # migration output.
+    for key in _OBSOLETE:
+        row = conn.execute(
+            sa.select(_settings.c.value).where(_settings.c.key == key)
+        ).fetchone()
+        if row is None:
+            print(f"a6_delete {key}: absent", flush=True)
+            continue
+        print(f"a6_delete {key}: {row[0]!r}", flush=True)
+        conn.execute(sa.delete(_settings).where(_settings.c.key == key))
+
+
+def downgrade() -> None:
+    """No-op.
+
+    The deleted rows configured jobs this revision's code no longer registers,
+    and the tombstones already hold the values pre-A6 code needs. Recreating
+    them would restore nothing useful; the printed values above cover recovery.
+    """