Enhance knowledge base functionality and integrate S3 storage support

- Add new models for `KnowledgeDocument` and `KnowledgeChunk` to manage document ingestion and chunking.
- Implement S3-compatible storage integration for knowledge documents, allowing for file uploads and retrieval.
- Introduce API endpoints for managing knowledge bases and documents, including creation, deletion, and searching.
- Update frontend components to support knowledge base configuration and document management, improving user interaction.
- Enhance backend services for knowledge processing and retrieval, ensuring robust handling of document statuses and errors.

backend/tests/test_knowledge.py

@@ -0,0 +1,23 @@
+import unittest
+
+from services.knowledge import extract_text, split_text
+
+
+class KnowledgeTextTest(unittest.TestCase):
+    def test_extracts_utf8_text(self):
+        self.assertEqual(extract_text("说明.txt", "你好，知识库".encode()), "你好，知识库")
+
+    def test_split_text_keeps_overlap_and_all_content(self):
+        text = "第一段。" * 250
+        chunks = split_text(text, chunk_size=120, overlap=20)
+        self.assertGreater(len(chunks), 1)
+        self.assertTrue(all(chunk for chunk in chunks))
+        self.assertLessEqual(max(map(len, chunks)), 120)
+
+    def test_rejects_unsupported_binary_file(self):
+        with self.assertRaisesRegex(ValueError, "暂仅支持"):
+            extract_text("archive.zip", b"data")
+
+
+if __name__ == "__main__":
+    unittest.main()