fix: guarantee shadow scan freshness, long-only, user-scoped setup list

Second review round on the shadow book; all three findings were real.

- Scan freshness is now proven, not assumed. Pipeline steps run and fail
  independently, so a disabled or failed scan step still let the shadow
  step run on the newest *stored* setups -- a prior session's picks at
  stale prices. scan_all_tickers now records a run boundary
  (last_scan_run_started_at / _completed_at) only on successful
  completion; the shadow book refuses to trade unless COMPLETED is fresh
  and selects only setups with detected_at >= the run start. Deduplication
  to the latest row per ticker now happens BEFORE qualification, so a newer
  unqualified row suppresses an older qualified one rather than the reverse.

- Shadow selection is hard long-only. setup_qualifies only enforces
  long-only when min_momentum_percentile > 0, but 0 is a legal admin
  setting, and the cash accounting assumes long positions -- so the
  constraint is enforced in shadow selection regardless of gate config.

- The personal setup list excludes only the caller's own open positions.
  get_trade_setups gained exclude_open_trade_user_id; the trades route
  passes the authenticated user, while the Telegram broadcast stays global
  since it has no single owner.

New tests cover stale/absent scan markers, prior-run exclusion, newer
unqualified suppressing older qualified, long-only under a disabled gate,
and both sides of the user-scoped exclusion.

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

app/routers/trades.py

@@ -25,7 +25,7 @@ async def list_trade_setups(
         None,
         description="Filter by action: LONG_HIGH, LONG_MODERATE, SHORT_HIGH, SHORT_MODERATE, NEUTRAL",
     ),
-    _user=Depends(require_access),
+    user=Depends(require_access),
     db: AsyncSession = Depends(get_db),
 ) -> APIEnvelope:
     """Get latest trade setups with recommendation data."""
@@ -36,6 +36,7 @@ async def list_trade_setups(
         recommended_action=recommended_action,
         live_recommendation=True,
         exclude_open_trade_tickers=True,
+        exclude_open_trade_user_id=user.id,
         exclude_reentry_gate_locked_tickers=True,
     )