fix: 修复知识库页面三处问题：出处下拉为空、宽度跳动、表格列宽优化

frontend/src/pages/KnowledgeBase/KnowledgeBase.jsx

@@ -29,6 +29,7 @@ export default function KnowledgeBase() {
   const [treeData, setTreeData] = useState([])
   const [loading, setLoading] = useState(false)
   const [uploading, setUploading] = useState(false)
+  const [sources, setSources] = useState([]) // 出处下拉选项
   const [sourceTypeFilter, setSourceTypeFilter] = useState('')
   const [sourceDetailFilter, setSourceDetailFilter] = useState('')
   const [selectedTreeNode, setSelectedTreeNode] = useState(null) // { type, detail }
@@ -54,9 +55,20 @@ export default function KnowledgeBase() {
     }
   }
 
+  const fetchSources = async () => {
+    try {
+      const data = await knowledgeService.listSources()
+      // 接口返回 [{source: "航空知识 2026年第1期"}, ...]，提取 source 字段
+      setSources(data.map(s => s.source).filter(Boolean))
+    } catch {
+      // ignore
+    }
+  }
+
   useEffect(() => {
     fetchItems()
     fetchTree()
+    fetchSources()
   }, [sourceTypeFilter])
 
   // 上传
@@ -127,32 +139,37 @@ export default function KnowledgeBase() {
       title: '标题',
       dataIndex: 'title',
       key: 'title',
-      render: (text, record) => (
-        <span style={{ fontWeight: 500, color: '#3b4a3b' }}>{text}</span>
+      width: 240,
+      render: (text) => (
+        <span style={{ fontWeight: 500, color: '#3b4a3b', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', display: 'block' }}>{text}</span>
       ),
     },
     {
       title: '作者',
       dataIndex: 'author',
       key: 'author',
-      render: (val) => val || null,
+      width: 80,
+      render: (val) => val || '-',
     },
     {
       title: '播出/发表时间',
       dataIndex: 'publish_date',
       key: 'publish_date',
-      render: (val) => val || null,
+      width: 156,
+      render: (val) => val || '-',
     },
     {
       title: '出处',
       dataIndex: 'source_detail',
       key: 'source_detail',
+      width: 170,
       render: (val) => val || '-',
     },
     {
       title: '类型',
       dataIndex: 'source_type',
       key: 'source_type',
+      width: 88,
       render: (val) => (
         <Tag color="default" style={{ borderRadius: 8 }}>
           {SOURCE_TYPE_LABEL[val] || val}
@@ -163,11 +180,13 @@ export default function KnowledgeBase() {
       title: '入库时间',
       dataIndex: 'created_at',
       key: 'created_at',
-      render: (val) => val ? new Date(val).toLocaleString('zh-CN') : '-',
+      width: 140,
+      render: (val) => val ? new Date(val).toLocaleString('zh-CN', { hour12: false }).replace(' ', ' ') : '-',
     },
     {
       title: '操作',
       key: 'action',
+      width: 86,
       render: (_, record) => (
         <Popconfirm
           title="确认删除"
@@ -244,7 +263,7 @@ export default function KnowledgeBase() {
               />
               <Select
                 placeholder="按出处"
-                options={[{ label: '全部出处', value: '' }, ...(items.length ? [] : [])]}
+                options={[{ label: '全部出处', value: '' }, ...sources.map(s => ({ label: s, value: s }))]}
                 value={sourceDetailFilter}
                 onChange={val => { setSourceDetailFilter(val); setSelectedTreeNode(null) }}
                 style={{ width: 200 }}