feat: paper trading capital controls — add, withdraw, and full reset

Three distinct capital operations on the Trading Controls page:

- Set Capital: overwrites pool balances to a new amount (existing)
- Add/Withdraw: adjusts active pool by a delta without touching
  positions, orders, or history. Validates sufficient balance for
  withdrawals. Logged to reserve_pool_ledger as manual_adjustment.
- Reset Everything: nuclear option — deletes all positions, orders,
  trading decisions, stop levels, snapshots, backtests, notifications,
  and circuit breaker events, then resets capital fresh. Red button
  with double-confirmation dialog.

Backend: POST /api/trading/capital/adjust and POST /api/trading/reset
Frontend: CapitalCard rebuilt with three sections and confirmation UIs

frontend/src/api/tradingHooks.ts

@@ -309,6 +309,38 @@ export function useBacktestLaunch() {
   });
 }
 
+/** Full paper trading reset: clears all positions, orders, decisions, and resets capital. */
+export function useResetPaperTrading() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (initial_capital: number) =>
+      apiPost<{ reset: boolean; initial_capital: number; active_pool: number; reserve_pool: number }>(
+        'trading', '/api/trading/reset', { initial_capital },
+      ),
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: ['trading-status'] });
+      qc.invalidateQueries({ queryKey: ['trading-decisions'] });
+      qc.invalidateQueries({ queryKey: ['trading-metrics'] });
+      qc.invalidateQueries({ queryKey: ['trading-metrics-history'] });
+    },
+  });
+}
+
+/** Add or subtract capital from the active pool without resetting anything else. */
+export function useAdjustCapital() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (amount: number) =>
+      apiPost<{ adjusted: number; active_pool: number; reserve_pool: number; total_value: number }>(
+        'trading', '/api/trading/capital/adjust', { amount },
+      ),
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: ['trading-status'] });
+      qc.invalidateQueries({ queryKey: ['trading-metrics'] });
+    },
+  });
+}
+
 /** Update notification preferences. */
 export function useUpdateNotificationConfig() {
   const qc = useQueryClient();