fidelity: push per-fund manual snapshot instead of gains-offset DEPOSIT

PlanViewer's DisplayValuation.action JSON already gives us current
fund units + unit price; we were parsing it and throwing it away,
emitting only a single 'unrealised-gains-offset' DEPOSIT to make
Wealthfolio's totals match the dashboard. That hack double-counted
the gain as a cash contribution, hiding £35k of pension growth from
every contribution/growth/ROI panel.

New flow:
- FidelityPlanViewerProvider exposes last_holdings + last_total_contribution
  after fetch() drains.
- fidelity-ingest CLI converts to a ManualSnapshotPayload (cost basis
  allocated proportionally by current fund value share) and posts to
  WF /api/v1/snapshots/import. WF auto-creates unknown fund symbols
  with kind=INVESTMENT, quoteMode=MANUAL, quoteCcy=GBP.
- The gains-offset emission is removed entirely. Historical offset
  rows already in WF are corrected at the dashboard layer by the
  dav_corrected view shipped in infra@2841347e.

WealthfolioSink gains push_manual_snapshots() + ManualSnapshotPayload /
SnapshotPosition wire types. 11 sink tests (3 new) + 9 fidelity
provider tests (2 changed, 1 new) all green; mypy + ruff clean.

broker_sync/cli.py

@@ -438,6 +438,15 @@ def fidelity_ingest(
         sys.exit(2)
 
     async def _run() -> None:
+        from datetime import date as _date_t
+
+        from broker_sync.providers.fidelity_planviewer import (
+            ACCOUNT_ID as FID_ACCOUNT_ID,
+        )
+        from broker_sync.providers.fidelity_planviewer import (
+            fidelity_holdings_to_snapshot,
+        )
+
         sink = WealthfolioSink(
             base_url=wf_base_url,
             username=wf_username,
@@ -455,12 +464,31 @@ def fidelity_ingest(
             result = await sync_provider_to_wealthfolio(
                 provider=provider, sink=sink, dedup=dedup, since=since,
             )
+            # PlanViewer has no historical per-fund unit-price feed, so
+            # the Activity stream above only carries cash flows. The
+            # current-pot fund positions captured in the same scrape get
+            # pushed via /api/v1/snapshots/import so per-fund quantity +
+            # cost basis land in WF (and propagate to the wealth
+            # dashboard's Positions table via pg-sync).
+            snapshot_imported = 0
+            if provider.last_holdings:
+                snapshot = fidelity_holdings_to_snapshot(
+                    holdings=provider.last_holdings,
+                    total_real_contribution=provider.last_total_contribution,
+                    as_of=_date_t.today(),
+                )
+                if snapshot is not None:
+                    push_result = await sink.push_manual_snapshots(
+                        account_id=FID_ACCOUNT_ID, snapshots=[snapshot],
+                    )
+                    snapshot_imported = int(push_result.get("snapshotsImported", 0))
         finally:
             await sink.close()
         typer.echo(f"fidelity-ingest: fetched={result.fetched} "
                    f"new={result.new_after_dedup} "
                    f"imported={result.imported} "
-                   f"failed={result.failed}")
+                   f"failed={result.failed} "
+                   f"snapshots={snapshot_imported}")
         if result.failed > 0:
             sys.exit(1)