fix: resolve 48 lint errors in test files

- Remove whitespace from 22 blank lines (W293)
- Remove 6 unused imports (F401): os, Mock, MagicMock, Path
- Add missing imports for 12 test functions (F821): sanitize_filename, extract_remote_path, MagicMock
- Fix 1 unsorted import block (I001)

All ruff checks now pass successfully.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_filename_utils.py

@@ -425,6 +425,8 @@ class TestSanitizeFilenameEdgeCases:
 
     def test_handles_empty_string(self):
         """Test with empty string."""
+        from app.utils.filename_utils import sanitize_filename
+
         result = sanitize_filename("")
         # Should return a default document name
         assert "document_" in result
@@ -432,23 +434,31 @@ class TestSanitizeFilenameEdgeCases:
 
     def test_handles_only_periods(self):
         """Test with only periods."""
+        from app.utils.filename_utils import sanitize_filename
+
         result = sanitize_filename("...")
         # Should return a default document name
         assert "document_" in result
 
     def test_handles_only_dots(self):
         """Test with single dot."""
+        from app.utils.filename_utils import sanitize_filename
+
         result = sanitize_filename(".")
         # Should return a default document name
         assert "document_" in result
 
     def test_preserves_multiple_extensions(self):
         """Test that multiple extensions are preserved."""
+        from app.utils.filename_utils import sanitize_filename
+
         result = sanitize_filename("file.tar.gz")
         assert ".tar.gz" in result or "file_tar_gz" in result
 
     def test_removes_null_bytes(self):
         """Test that null bytes are removed."""
+        from app.utils.filename_utils import sanitize_filename
+
         result = sanitize_filename("file\x00name.pdf")
         assert "\x00" not in result
         assert "file" in result
@@ -456,6 +466,8 @@ class TestSanitizeFilenameEdgeCases:
 
     def test_handles_unicode_characters(self):
         """Test handling of unicode characters."""
+        from app.utils.filename_utils import sanitize_filename
+
         result = sanitize_filename("文档.pdf")
         # Should preserve unicode or convert safely
         assert ".pdf" in result
@@ -468,31 +480,39 @@ class TestExtractRemotePathEdgeCases:
 
     def test_file_not_in_base_dir(self):
         """Test when file is not a subdirectory of base_dir."""
+        from app.utils.filename_utils import extract_remote_path
+
         result = extract_remote_path("/other/path/file.pdf", "/base/dir", "/remote")
         # Should just use filename
         assert result == "remote/file.pdf"
 
     def test_multiple_processed_directories(self):
         """Test path with multiple 'processed' directories."""
-        result = extract_remote_path(
-            "/base/processed/subdir/processed/file.pdf", "/base", "/remote"
-        )
+        from app.utils.filename_utils import extract_remote_path
+
+        result = extract_remote_path("/base/processed/subdir/processed/file.pdf", "/base", "/remote")
         # Should remove all 'processed' directories
         assert "processed" not in result.lower()
 
     def test_remote_base_with_trailing_slash(self):
         """Test remote base that already has trailing slash."""
+        from app.utils.filename_utils import extract_remote_path
+
         result = extract_remote_path("/base/file.pdf", "/base", "/remote/")
         # Should handle gracefully
         assert result.startswith("remote/")
 
     def test_empty_remote_base(self):
         """Test with empty remote base."""
+        from app.utils.filename_utils import extract_remote_path
+
         result = extract_remote_path("/base/subdir/file.pdf", "/base", "")
         assert result == "subdir/file.pdf"
 
     def test_windows_style_separators(self, monkeypatch):
         """Test handling of Windows-style path separators."""
+        from app.utils.filename_utils import extract_remote_path
+
         result = extract_remote_path("/base/subdir/file.pdf", "/base", "/remote")
         # Should use forward slashes in output
         assert "\\" not in result