Add per-firm banned symbols feature

- lib/db.ts: new firm_banned_symbols table with getBannedSymbols,
  isSymbolBanned, and setBannedSymbol helpers
- app/api/firms/[id]/banned-symbols/route.ts: GET lists banned symbols,
  PATCH toggles a ban for a given symbol
- app/api/firms/route.ts: include bannedSymbols[] in firm list response
- app/firms/[id]/settings/page.tsx: Instruments section shows all
  globally-enabled symbols with a red toggle to ban/unban; banned
  symbols display a "SYMBOL BANNED" pill next to their name
- app/page.tsx: FirmRows shows "ES BANNED" (or current symbol) pill next
  to the firm name when the selected trade symbol is banned for that firm
- lib/auto-trade.ts: skip firms entirely when the trade symbol is banned
- types.ts: add bannedSymbols field to FirmConfig

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/auto-trade.ts

@@ -7,7 +7,7 @@
  * signal but have since exited and are now eligible.
  */
 
-import { getFirms } from './db';
+import { getFirms, isSymbolBanned } from './db';
 import { getClients } from './clients';
 import { computeDailyTarget, POINT_VALUES } from './trading-logic';
 import { getSetting } from './db';
@@ -100,6 +100,12 @@ export async function runTrade(action: 'Buy' | 'Sell' | 'Random', symbol: string
         const client = clients.get(firm.id);
         if (!client || client.accountList.length === 0) return;
 
+        // Skip this firm entirely if the symbol is banned for it
+        if (isSymbolBanned(firm.id, symbol)) {
+            console.log(`[auto-trade] ${firm.name}: ${symbol} is banned — skipping firm`);
+            return;
+        }
+
         const firmConfig = mapFirmConfig(firm);
 
         const contract = await client.findFrontMonthContract(symbol);