Add trailing stops and parameter sweeps

Trailing stops: strategies can pass trailing_stop_pct to enter_long/enter_short.
advance_trailing_stop in app/engine/portfolio.py ratchets the stop with the price
(up for longs, down for shorts) and never loosens; the engine persists the
ratcheted level and the backtester applies the same logic. Position gains a
trailing_stop_pct column (additive migration). momentum exposes it as a param.

Parameter sweeps: app/backtest/sweep.py runs a cartesian grid through the same
backtester and ranks by return minus max drawdown. POST /api/sweep plus a
dashboard Parameter sweep panel.

frontend/src/App.vue

@@ -8,6 +8,7 @@ import OrdersTable from './components/OrdersTable.vue'
 import PositionsTable from './components/PositionsTable.vue'
 import StatusCards from './components/StatusCards.vue'
 import StrategyPanel from './components/StrategyPanel.vue'
+import SweepPanel from './components/SweepPanel.vue'
 
 const status = ref({
   running: false,
@@ -196,6 +197,7 @@ onUnmounted(() => {
     />
 
     <BacktestPanel :strategies="strategies" :status="status" />
+    <SweepPanel :strategies="strategies" :status="status" />
 
     <div class="grid gap-4 lg:grid-cols-2">
       <EquityChart :points="equityPoints" />

frontend/src/api.js

@@ -19,6 +19,9 @@ export const placeOrder = (payload) => http.post('/orders', payload).then((r) =>
 export const runBacktest = (payload) =>
   http.post('/backtest', payload, { timeout: 60000 }).then((r) => r.data)
 
+export const runSweep = (payload) =>
+  http.post('/sweep', payload, { timeout: 120000 }).then((r) => r.data)
+
 export const getPresets = () => http.get('/presets').then((r) => r.data)
 export const createPreset = (payload) => http.post('/presets', payload).then((r) => r.data)
 export const deletePreset = (id) => http.delete(`/presets/${id}`).then((r) => r.data)

frontend/src/components/SweepPanel.vue

@@ -0,0 +1,172 @@
+<script setup>
+import { computed, ref, watch } from 'vue'
+import * as api from '../api'
+import { fmtMoney, pnlClass, signed } from '../format'
+
+const props = defineProps({
+  strategies: { type: Array, required: true },
+  status: { type: Object, required: true },
+})
+
+const running = ref(false)
+const error = ref(null)
+const result = ref(null)
+const selectedKey = ref('')
+const limit = ref(500)
+const topN = ref(20)
+const symbol = ref(props.status.symbol || 'BTC/USDT')
+const timeframe = ref(props.status.timeframe || '5m')
+// param name -> comma-separated candidate values
+const gridText = ref({})
+
+const selected = computed(() => props.strategies.find((s) => s.key === selectedKey.value))
+
+watch(
+  () => props.strategies,
+  (list) => {
+    if (!selectedKey.value && list.length) selectedKey.value = list[0].key
+  },
+  { immediate: true },
+)
+
+watch(selected, (strategy) => {
+  gridText.value = {}
+  if (strategy) {
+    // Seed each numeric param with a sensible two-value grid.
+    for (const p of strategy.params) {
+      if (p.type === 'int' || p.type === 'float') {
+        const v = Number(p.default)
+        gridText.value[p.name] = `${v},${p.type === 'int' ? v * 2 : (v * 2).toFixed(4)}`
+      }
+    }
+  }
+})
+
+function buildGrid() {
+  const grid = {}
+  for (const [name, raw] of Object.entries(gridText.value)) {
+    const values = String(raw)
+      .split(',')
+      .map((x) => x.trim())
+      .filter((x) => x !== '')
+      .map((x) => Number(x))
+      .filter((x) => !Number.isNaN(x))
+    if (values.length) grid[name] = values
+  }
+  return grid
+}
+
+async function run() {
+  running.value = true
+  error.value = null
+  try {
+    const grid = buildGrid()
+    if (!Object.keys(grid).length) {
+      error.value = 'Provide at least one parameter with candidate values.'
+      return
+    }
+    result.value = await api.runSweep({
+      strategy_key: selectedKey.value,
+      base_params: {},
+      grid,
+      symbol: symbol.value,
+      timeframe: timeframe.value,
+      limit: Number(limit.value),
+      top_n: Number(topN.value),
+    })
+    if (result.value.error) error.value = result.value.error
+  } catch (e) {
+    error.value = e.response?.data?.detail || e.message
+  } finally {
+    running.value = false
+  }
+}
+</script>
+
+<template>
+  <div class="card space-y-3">
+    <div class="flex items-center justify-between">
+      <h2 class="font-semibold">Parameter sweep</h2>
+      <span v-if="result" class="text-xs text-slate-400">
+        {{ result.combinations }} combinations · top {{ result.rows.length }}
+      </span>
+    </div>
+
+    <div class="grid gap-2 sm:grid-cols-4">
+      <label class="space-y-1">
+        <span class="label">Strategy</span>
+        <select v-model="selectedKey" class="input" :disabled="running">
+          <option v-for="s in strategies" :key="s.key" :value="s.key">{{ s.name }}</option>
+        </select>
+      </label>
+      <label class="space-y-1">
+        <span class="label">Symbol</span>
+        <input v-model="symbol" class="input" :disabled="running" />
+      </label>
+      <label class="space-y-1">
+        <span class="label">Timeframe</span>
+        <input v-model="timeframe" class="input" :disabled="running" />
+      </label>
+      <label class="space-y-1">
+        <span class="label">Candles</span>
+        <input v-model="limit" type="number" min="20" max="1000" class="input" :disabled="running" />
+      </label>
+    </div>
+
+    <div v-if="selected" class="grid gap-2 sm:grid-cols-2 lg:grid-cols-3">
+      <label v-for="(raw, name) in gridText" :key="name" class="space-y-1">
+        <span class="label">{{ name }} (comma-separated)</span>
+        <input v-model="gridText[name]" class="input" :disabled="running" />
+      </label>
+    </div>
+
+    <div class="flex items-center gap-2">
+      <label class="flex items-center gap-2 text-sm text-slate-300">
+        Top N
+        <input v-model="topN" type="number" min="1" max="100" class="input w-20" :disabled="running" />
+      </label>
+      <button class="btn-primary" :disabled="running || !selectedKey" @click="run">
+        {{ running ? 'Running…' : 'Run sweep' }}
+      </button>
+    </div>
+
+    <p v-if="error" class="rounded-lg border border-rose-500/40 bg-rose-500/10 p-3 text-sm text-rose-200">
+      {{ error }}
+    </p>
+
+    <div v-if="result && result.rows.length" class="overflow-x-auto">
+      <table class="w-full text-left text-sm">
+        <thead class="label">
+          <tr>
+            <th class="pb-2">#</th>
+            <th class="pb-2">Params</th>
+            <th class="pb-2 text-right">Return</th>
+            <th class="pb-2 text-right">Max DD</th>
+            <th class="pb-2 text-right">Trades</th>
+            <th class="pb-2 text-right">Win rate</th>
+            <th class="pb-2 text-right">Sharpe</th>
+          </tr>
+        </thead>
+        <tbody>
+          <tr v-for="(row, i) in result.rows" :key="i" class="border-t border-edge/60">
+            <td class="py-1.5 text-slate-400">{{ i + 1 }}</td>
+            <td class="py-1.5 font-mono text-xs">
+              <span v-for="(v, k) in row.params" :key="k" class="mr-2">{{ k }}={{ v }}</span>
+            </td>
+            <td class="py-1.5 text-right tabular-nums" :class="pnlClass(row.metrics.total_return_pct)">
+              {{ signed(row.metrics.total_return_pct) }}%
+            </td>
+            <td class="py-1.5 text-right tabular-nums text-amber-300">
+              -{{ fmtMoney(row.metrics.max_drawdown_pct) }}%
+            </td>
+            <td class="py-1.5 text-right tabular-nums">{{ row.metrics.num_trades }}</td>
+            <td class="py-1.5 text-right tabular-nums">{{ fmtMoney(row.metrics.win_rate_pct) }}%</td>
+            <td class="py-1.5 text-right tabular-nums">
+              {{ row.metrics.sharpe === null ? '—' : fmtMoney(row.metrics.sharpe) }}
+            </td>
+          </tr>
+        </tbody>
+      </table>
+    </div>
+  </div>
+</template>