feat: migrate ORM base to sqlmodel-ext, add file viewers and WOPI integration

- Migrate SQLModel base classes, mixins, and database management to
  external sqlmodel-ext package; remove sqlmodels/base/, sqlmodels/mixin/,
  and sqlmodels/database.py
- Add file viewer/editor system with WOPI protocol support for
  collaborative editing (OnlyOffice, Collabora)
- Add enterprise edition license verification module (ee/)
- Add Dockerfile multi-stage build with Cython compilation support
- Add new dependencies: sqlmodel-ext, cryptography, whatthepatch

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

tests/unit/utils/test_patch.py

@@ -0,0 +1,178 @@
+"""
+文本文件 patch 逻辑单元测试
+
+测试 whatthepatch 库的 patch 解析与应用，
+以及换行符规范化和 SHA-256 哈希计算。
+"""
+import hashlib
+
+import pytest
+import whatthepatch
+from whatthepatch.exceptions import HunkApplyException
+
+
+class TestPatchApply:
+    """测试 patch 解析与应用"""
+
+    def test_normal_patch(self) -> None:
+        """正常 patch 应用"""
+        original = "line1\nline2\nline3"
+        patch_text = (
+            "--- a\n"
+            "+++ b\n"
+            "@@ -1,3 +1,3 @@\n"
+            " line1\n"
+            "-line2\n"
+            "+LINE2\n"
+            " line3\n"
+        )
+
+        diffs = list(whatthepatch.parse_patch(patch_text))
+        assert len(diffs) == 1
+
+        result = whatthepatch.apply_diff(diffs[0], original)
+        new_text = '\n'.join(result)
+
+        assert "LINE2" in new_text
+        assert "line2" not in new_text
+
+    def test_add_lines_patch(self) -> None:
+        """添加行的 patch"""
+        original = "line1\nline2"
+        patch_text = (
+            "--- a\n"
+            "+++ b\n"
+            "@@ -1,2 +1,3 @@\n"
+            " line1\n"
+            " line2\n"
+            "+line3\n"
+        )
+
+        diffs = list(whatthepatch.parse_patch(patch_text))
+        result = whatthepatch.apply_diff(diffs[0], original)
+        new_text = '\n'.join(result)
+
+        assert "line3" in new_text
+
+    def test_delete_lines_patch(self) -> None:
+        """删除行的 patch"""
+        original = "line1\nline2\nline3"
+        patch_text = (
+            "--- a\n"
+            "+++ b\n"
+            "@@ -1,3 +1,2 @@\n"
+            " line1\n"
+            "-line2\n"
+            " line3\n"
+        )
+
+        diffs = list(whatthepatch.parse_patch(patch_text))
+        result = whatthepatch.apply_diff(diffs[0], original)
+        new_text = '\n'.join(result)
+
+        assert "line2" not in new_text
+        assert "line1" in new_text
+        assert "line3" in new_text
+
+    def test_invalid_patch_format(self) -> None:
+        """无效的 patch 格式返回空列表"""
+        diffs = list(whatthepatch.parse_patch("this is not a patch"))
+        assert len(diffs) == 0
+
+    def test_patch_context_mismatch(self) -> None:
+        """patch 上下文不匹配时抛出异常"""
+        original = "line1\nline2\nline3\n"
+        patch_text = (
+            "--- a\n"
+            "+++ b\n"
+            "@@ -1,3 +1,3 @@\n"
+            " line1\n"
+            "-WRONG\n"
+            "+REPLACED\n"
+            " line3\n"
+        )
+
+        diffs = list(whatthepatch.parse_patch(patch_text))
+        with pytest.raises(HunkApplyException):
+            whatthepatch.apply_diff(diffs[0], original)
+
+    def test_empty_file_patch(self) -> None:
+        """空文件应用 patch"""
+        original = ""
+        patch_text = (
+            "--- a\n"
+            "+++ b\n"
+            "@@ -0,0 +1,2 @@\n"
+            "+line1\n"
+            "+line2\n"
+        )
+
+        diffs = list(whatthepatch.parse_patch(patch_text))
+        result = whatthepatch.apply_diff(diffs[0], original)
+        new_text = '\n'.join(result)
+
+        assert "line1" in new_text
+        assert "line2" in new_text
+
+
+class TestHashComputation:
+    """测试 SHA-256 哈希计算"""
+
+    def test_hash_consistency(self) -> None:
+        """相同内容产生相同哈希"""
+        content = "hello world\n"
+        content_bytes = content.encode('utf-8')
+        hash1 = hashlib.sha256(content_bytes).hexdigest()
+        hash2 = hashlib.sha256(content_bytes).hexdigest()
+
+        assert hash1 == hash2
+        assert len(hash1) == 64
+
+    def test_hash_differs_for_different_content(self) -> None:
+        """不同内容产生不同哈希"""
+        hash1 = hashlib.sha256(b"content A").hexdigest()
+        hash2 = hashlib.sha256(b"content B").hexdigest()
+
+        assert hash1 != hash2
+
+    def test_hash_after_normalization(self) -> None:
+        """换行符规范化后的哈希一致性"""
+        content_crlf = "line1\r\nline2\r\n"
+        content_lf = "line1\nline2\n"
+
+        # 规范化后应相同
+        normalized = content_crlf.replace('\r\n', '\n').replace('\r', '\n')
+        assert normalized == content_lf
+
+        hash_normalized = hashlib.sha256(normalized.encode('utf-8')).hexdigest()
+        hash_lf = hashlib.sha256(content_lf.encode('utf-8')).hexdigest()
+
+        assert hash_normalized == hash_lf
+
+
+class TestLineEndingNormalization:
+    """测试换行符规范化"""
+
+    def test_crlf_to_lf(self) -> None:
+        """CRLF 转换为 LF"""
+        content = "line1\r\nline2\r\n"
+        normalized = content.replace('\r\n', '\n').replace('\r', '\n')
+        assert normalized == "line1\nline2\n"
+
+    def test_cr_to_lf(self) -> None:
+        """CR 转换为 LF"""
+        content = "line1\rline2\r"
+        normalized = content.replace('\r\n', '\n').replace('\r', '\n')
+        assert normalized == "line1\nline2\n"
+
+    def test_lf_unchanged(self) -> None:
+        """LF 保持不变"""
+        content = "line1\nline2\n"
+        normalized = content.replace('\r\n', '\n').replace('\r', '\n')
+        assert normalized == content
+
+    def test_mixed_line_endings(self) -> None:
+        """混合换行符统一为 LF"""
+        content = "line1\r\nline2\rline3\n"
+        normalized = content.replace('\r\n', '\n').replace('\r', '\n')
+        assert normalized == "line1\nline2\nline3\n"