feat(ui): replace native confirm() with DaisyUI modal composable (F7.2)

Create useConfirm composable (promise-based, singleton state) and
ConfirmModal component. Replace all 10 confirm()/window.confirm() calls
across 9 pages and 1 composable.

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

app/components/common/ConfirmModal.vue

@@ -0,0 +1,41 @@
+<template>
+  <teleport to="body">
+    <div
+      v-if="confirmState.open"
+      class="fixed inset-0 z-[1200] flex items-center justify-center bg-black/60 backdrop-blur-sm"
+      @click.self="handleCancel"
+    >
+      <div class="bg-base-100 rounded-box shadow-xl w-full max-w-md mx-4 p-6 space-y-4">
+        <h3 class="font-bold text-lg">
+          {{ confirmState.title }}
+        </h3>
+
+        <p class="whitespace-pre-line text-base-content/80">
+          {{ confirmState.message }}
+        </p>
+
+        <div class="flex justify-end gap-2 pt-2">
+          <button
+            class="btn btn-ghost btn-sm"
+            @click="handleCancel"
+          >
+            {{ confirmState.cancelText }}
+          </button>
+          <button
+            class="btn btn-sm"
+            :class="confirmState.dangerous ? 'btn-error' : 'btn-primary'"
+            @click="handleConfirm"
+          >
+            {{ confirmState.confirmText }}
+          </button>
+        </div>
+      </div>
+    </div>
+  </teleport>
+</template>
+
+<script setup lang="ts">
+import { useConfirm } from '~/composables/useConfirm'
+
+const { confirmState, handleConfirm, handleCancel } = useConfirm()
+</script>