feat: 收口知识库分享链路

- 新增 shareKey 单参数 URL 分享页与失效页

- 新增知识库分享后端鉴权、审计与迁移脚本

- 在访问令牌中增加知识库分享授权入口

easyflow-ui-admin/app/src/views/ai/documentCollection/KnowledgeShareExpired.vue

@@ -0,0 +1,60 @@
+<script setup lang="ts">
+import { computed } from 'vue';
+import { useRoute } from 'vue-router';
+
+const route = useRoute();
+
+const isInvalid = computed(() => route.query.reason === 'invalid');
+const title = computed(() => (isInvalid.value ? '链接无效' : '链接已过期'));
+const description = computed(() =>
+  isInvalid.value
+    ? '请确认链接完整无误，或联系分享人重新生成。'
+    : '请联系分享人重新生成可用链接。',
+);
+</script>
+
+<template>
+  <div class="share-expired">
+    <div class="share-expired__card">
+      <div class="share-expired__title">{{ title }}</div>
+      <div class="share-expired__desc">{{ description }}</div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.share-expired {
+  display: grid;
+  place-items: center;
+  min-height: 100vh;
+  padding: 24px;
+  background:
+    radial-gradient(
+      circle at top left,
+      rgb(255 240 240 / 88%),
+      transparent 28%
+    ),
+    linear-gradient(180deg, #faf7f6 0%, #f3efed 100%);
+}
+
+.share-expired__card {
+  width: min(460px, 100%);
+  padding: 36px 28px;
+  text-align: center;
+  background: rgb(255 255 255 / 92%);
+  border: 1px solid rgb(220 227 235 / 72%);
+  border-radius: 24px;
+}
+
+.share-expired__title {
+  font-size: 30px;
+  font-weight: 700;
+  letter-spacing: -0.02em;
+}
+
+.share-expired__desc {
+  margin-top: 12px;
+  font-size: 14px;
+  color: var(--el-text-color-secondary);
+}
+</style>