feat: ticker search, watchlist momentum column, alpha vs S&P 500

Three usability fixes:

1. Global ticker search in the sidebar (TickerSearch) — typeahead over the
   tracked universe that opens a ticker's detail page without adding it to the
   watchlist. Also wired into the mobile nav.

2. Watchlist table shows the ticker's 12-1 momentum percentile (the top-pick
   selector) instead of the noisy full S/R-level list. Enriched from the setup
   already loaded in watchlist_service._enrich_entry — no extra query.

3. Alpha vs the S&P 500 on paper trades (open + closed). New benchmark_prices
   table + benchmark_service store SPY daily closes (a standalone series, not a
   Ticker, so it never enters the scanner / momentum ranking / rankings) via a
   new daily-pipeline step. paper_trade_service computes per-trade
   benchmark_return / alpha_pct / alpha_usd over each holding period; the open-
   trades table, dashboard, and closed-trades panel surface per-trade and total
   alpha. The list read path never makes a provider call.

Deploy: alembic upgrade head, then run the benchmark/daily job once to populate
SPY closes (alpha shows "—" until then).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_watchlist_service.py

@@ -60,6 +60,25 @@ async def _make_ticker(session, symbol: str, *, score: float | None = None) -> i
     return t.id
 
 
+async def test_enrich_includes_momentum_percentile(session):
+    """The watchlist row carries the ticker's momentum percentile (from its setup),
+    which replaces the old S/R-levels column in the UI."""
+    from app.models.trade_setup import TradeSetup
+
+    user_id = await _make_user(session)
+    tid = await _make_ticker(session, "AAA", score=70.0)
+    session.add(TradeSetup(
+        ticker_id=tid, direction="long", entry_price=100.0, stop_loss=95.0,
+        target=110.0, rr_ratio=2.0, composite_score=70.0,
+        momentum_percentile=88.0, detected_at=datetime.now(timezone.utc),
+    ))
+    await session.commit()
+
+    await add_manual_entry(session, user_id, "AAA")
+    rows = await get_watchlist(session, user_id)
+    assert rows[0]["momentum_percentile"] == 88.0
+
+
 async def test_add_and_remove_sticks(session):
     user_id = await _make_user(session)
     await _make_ticker(session, "AAA", score=80.0)