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>

alembic/versions/011_add_benchmark_prices.py

@@ -0,0 +1,41 @@
+"""add benchmark_prices
+
+Stores daily closes for a benchmark index (SPY) so paper-trade alpha — trade
+return minus the benchmark's return over the same holding period — can be
+computed. Kept separate from the tradeable universe: the benchmark is not a
+Ticker, so it never enters the scanner, momentum ranking, or rankings.
+
+Revision ID: 011
+Revises: 010
+Create Date: 2026-06-28 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = "011"
+down_revision: Union[str, None] = "010"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "benchmark_prices",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("symbol", sa.String(length=20), nullable=False),
+        sa.Column("date", sa.Date(), nullable=False),
+        sa.Column("close", sa.Float(), nullable=False),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint("symbol", "date", name="uq_benchmark_symbol_date"),
+    )
+    op.create_index("ix_benchmark_prices_symbol", "benchmark_prices", ["symbol"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_benchmark_prices_symbol", table_name="benchmark_prices")
+    op.drop_table("benchmark_prices")