feat(pricing): introduce real-time budget estimator

This commit introduces a real-time budget estimator for event services. A new summary sidebar now displays a live,
itemized breakdown of costs as the user selects options in the order form.

Key changes include:
- A new `OrderSummary` component to display the price breakdown and total.
- Comprehensive pricing logic implemented in the `useEventOrder` composable.
- A responsive two-column layout on the main page to accommodate the summary.
- UI/UX improvements across the form, including clearer labels and subtle transition animations for conditional fields.

app/components/eventOrder/OrderSummary.vue

@@ -0,0 +1,77 @@
+<template>
+  <UCard class="lg:sticky lg:top-24">
+    <template #header>
+      <div class="flex items-center justify-between">
+        <h2 class="text-xl font-bold">预算估算</h2>
+        <UBadge color="primary" variant="soft">实时</UBadge>
+      </div>
+      <p class="text-muted text-sm">基于所选服务动态计算</p>
+    </template>
+
+    <div class="space-y-3">
+      <div v-if="items.length === 0" class="text-muted text-sm">
+        当前未选择任何可计价项目。
+      </div>
+      <div v-else class="space-y-3">
+        <div
+          v-for="(it, idx) in items"
+          :key="idx"
+          class="flex items-start justify-between gap-3 border-b border-[--ui-border] pb-2"
+        >
+          <div>
+            <div class="font-medium">{{ it.label }}</div>
+            <div v-if="it.note" class="text-muted text-xs">{{ it.note }}</div>
+          </div>
+          <div class="font-semibold">{{ money.format(it.amount) }}</div>
+        </div>
+      </div>
+    </div>
+
+    <template #footer>
+      <div class="flex items-center justify-between">
+        <div class="text-lg font-bold">合计</div>
+        <div class="text-2xl font-extrabold tracking-tight">
+          {{ money.format(total) }}
+        </div>
+      </div>
+      <div class="mt-3 flex items-center gap-2">
+        <UButton
+          color="primary"
+          size="lg"
+          block
+          :disabled="total === 0"
+          icon="lucide:send"
+          @click="onRequestQuote"
+        >
+          获取详细报价
+        </UButton>
+      </div>
+      <UAlert
+        class="mt-3"
+        title="说明"
+        color="neutral"
+        variant="subtle"
+        description="该预算为参考价，具体以需求细化及工期排期为准。"
+      />
+    </template>
+  </UCard>
+</template>
+
+<script lang="ts" setup>
+const { priceBreakdown, estimatedTotal, money } = useEventOrder();
+
+const items = computed(() => priceBreakdown.value);
+const total = computed(() => estimatedTotal.value);
+
+function onRequestQuote() {
+  // Placeholder interaction (no backend). Could open mailto or copy summary.
+  const lines = items.value.map(
+    (i) =>
+      `${i.label}：${money.format(i.amount)}${i.note ? `（${i.note}）` : ""}`
+  );
+  const text = `预算合计：${money.format(total.value)}\n\n` + lines.join("\n");
+  if (navigator?.clipboard) navigator.clipboard.writeText(text).catch(() => {});
+}
+</script>
+
+<style></style>