Multi-ticker historical backtests: ticker filter + per-coin grouping

- Historical cards now deduplicated by strategy+ticker (28 entries: 7×4)
- Ticker filter bar: ALL | BTC | ETH | HYPE | VVV
- Coin badge on each card
- BacktestSummary.coin now required string field
- fetchHistorical groups by strategy · coin composite key

dashboard-next/src/lib/api.ts

@@ -82,7 +82,8 @@ export async function fetchHistorical(): Promise<Record<string, import("./types"
   const list: import("./types").BacktestSummary[] = await res.json();
   const byStrat: Record<string, import("./types").BacktestSummary> = {};
   for (const b of list) {
-    if (!byStrat[b.strategy]) byStrat[b.strategy] = b;
+    const key = `${b.strategy} · ${b.coin ?? "?"}`;
+    if (!byStrat[key]) byStrat[key] = b;
   }
   return byStrat;
 }

dashboard-next/src/lib/types.ts

@@ -93,7 +93,7 @@ export interface BacktestSummary {
   max_dd: number;
   win_rate: number;
   total_trades: number;
-  coin?: string;
+  coin: string;
 }
 
 export interface BacktestFull {