Add daily target logic and consistency reference line to equity curve

- lib/trading-logic.ts: computeDailyTarget() computes the next trading
  day's profit target via two paths:
  • No positive days yet → profitTarget × consistency (first day)
  • Positive days exist → maxDay / consistency gives the total profit
    needed to satisfy the consistency rule; target maxDay when far away,
    or the exact remaining amount when close
- Account detail page: display "Next Trading Day Amount" in Objectives card
- Equity curve: add indigo dashed reference line for the consistency target
  (maxDay / consistency), labelled top-left to avoid overlapping the amber
  profit-target line (top-right)

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

lib/trading-logic.ts

@@ -0,0 +1,38 @@
+/**
+ * Compute the next trading day's profit target for an account.
+ *
+ * Path 1 – No positive trading days yet:
+ *   target = profitTarget × consistency
+ *
+ * Path 2 – At least one positive day exists:
+ *   maxDay     = highest single-day P&L so far
+ *   realTarget = maxDay / consistency  (the total profit at which maxDay ≤ consistency% of total)
+ *   needed     = realTarget − totalProfit
+ *
+ *   if needed > maxDay  → target maxDay (still a long way from the real target; trade a normal day)
+ *   else                → target needed (close to the real target; aim for exactly what's left)
+ */
+export function computeDailyTarget(
+    profitTarget: number,
+    consistency: number,
+    totalProfit: number,
+    dailyPnL: { date: string; pnl: number }[]
+): { amount: number; path: 'first_day' | 'normal_day' | 'reduced_day' } {
+    const positiveDays = dailyPnL.filter((d) => d.pnl > 0);
+
+    if (positiveDays.length === 0) {
+        return {
+            amount: Math.round(profitTarget * consistency * 100) / 100,
+            path: 'first_day',
+        };
+    }
+
+    const maxDay = Math.max(...positiveDays.map((d) => d.pnl));
+    const realTarget = maxDay / consistency;
+    const needed = realTarget - totalProfit;
+
+    if (needed > maxDay) {
+        return { amount: Math.round(maxDay * 100) / 100, path: 'normal_day' };
+    }
+    return { amount: Math.round(Math.max(0, needed) * 100) / 100, path: 'reduced_day' };
+}