fix: resolve multiple bugs preventing trader creation (#1138)

* fix: resolve multiple bugs preventing trader creation
Bug fixes:
1. Fix time.Time scanning error - SQLite stores datetime as TEXT, now parsing manually
2. Fix foreign key mismatch - traders table referenced exchanges(id) but exchanges uses composite primary key (id, user_id)
3. Add missing backtestManager field to Server struct
4. Add missing Shutdown method to Server struct
5. Fix NewFuturesTrader call - pass userId parameter
6. Fix UpdateExchange call - pass all required parameters
7. Add migrateTradersTable() to fix existing databases
These issues prevented creating new traders with 500 errors.
* fix(api): fix balance extraction field name mismatch
Binance API returns 'availableBalance' (camelCase) but code was looking for
'available_balance' (snake_case). Now supports both formats.
Also added 'totalWalletBalance' as fallback for total balance extraction.
* fix(frontend): add missing ConfirmDialogProvider to App
The delete trader button required ConfirmDialogProvider to be wrapped
around the App component for the confirmation dialog to work.
---------
Co-authored-by: NOFX Trader <nofx@local.dev>

web/src/App.tsx

@@ -13,6 +13,7 @@ import HeaderBar from './components/HeaderBar'
 import AILearning from './components/AILearning'
 import { LanguageProvider, useLanguage } from './contexts/LanguageContext'
 import { AuthProvider, useAuth } from './contexts/AuthContext'
+import { ConfirmDialogProvider } from './components/ConfirmDialog'
 import { t, type Language } from './i18n/translations'
 import { useSystemConfig } from './hooks/useSystemConfig'
 import { DecisionCard } from './components/DecisionCard'
@@ -1062,7 +1063,9 @@ export default function AppWithProviders() {
   return (
     <LanguageProvider>
       <AuthProvider>
-        <App />
+        <ConfirmDialogProvider>
+          <App />
+        </ConfirmDialogProvider>
       </AuthProvider>
     </LanguageProvider>
   )