Add OCR, Background Removal, and PDF Editor features with tests

- Implemented OCR functionality using pytesseract for image and PDF text extraction.
- Added Background Removal service using rembg for image processing.
- Developed PDF Editor service for applying text annotations to PDF files.
- Created corresponding API routes for OCR, Background Removal, and PDF Editor.
- Added frontend components for OCR and Background Removal tools.
- Integrated feature flagging for new tools, ensuring they are disabled by default.
- Implemented comprehensive unit tests for OCR service, PDF editor, and background removal.
- Updated documentation to reflect new features and usage instructions.
- Added translations for new features in English, Arabic, and French.

backend/tests/test_ocr_service.py

@@ -0,0 +1,66 @@
+"""Tests for OCR service and PDF editor service — unit tests with mocking."""
+import os
+import sys
+import tempfile
+
+import pytest
+from unittest.mock import patch, MagicMock
+
+from app.services.ocr_service import ocr_image, OCRError, SUPPORTED_LANGUAGES
+
+
+class TestOcrServiceConstants:
+    def test_supported_languages(self):
+        """Verify the supported languages dict."""
+        assert "eng" in SUPPORTED_LANGUAGES
+        assert "ara" in SUPPORTED_LANGUAGES
+        assert "fra" in SUPPORTED_LANGUAGES
+        assert len(SUPPORTED_LANGUAGES) == 3
+
+
+class TestOcrImage:
+    def test_ocr_image_success(self):
+        """Should return text and char_count from image (mocked pytesseract)."""
+        mock_pytesseract = MagicMock()
+        mock_pytesseract.image_to_string.return_value = "  Hello World  "
+        mock_pytesseract.pytesseract.tesseract_cmd = ""
+
+        mock_img = MagicMock()
+        mock_img.mode = "RGB"
+        mock_img.__enter__ = MagicMock(return_value=mock_img)
+        mock_img.__exit__ = MagicMock(return_value=False)
+
+        with patch.dict(sys.modules, {"pytesseract": mock_pytesseract}):
+            with patch("app.services.ocr_service.Image") as mock_pil:
+                mock_pil.open.return_value = mock_img
+                result = ocr_image("/fake/path.png", lang="eng")
+
+        assert result["text"] == "Hello World"
+        assert result["char_count"] == 11
+        assert result["lang"] == "eng"
+
+    def test_ocr_image_invalid_lang_fallback(self):
+        """Invalid language should fall back to 'eng'."""
+        mock_pytesseract = MagicMock()
+        mock_pytesseract.image_to_string.return_value = "Test"
+        mock_pytesseract.pytesseract.tesseract_cmd = ""
+
+        mock_img = MagicMock()
+        mock_img.mode = "RGB"
+        mock_img.__enter__ = MagicMock(return_value=mock_img)
+        mock_img.__exit__ = MagicMock(return_value=False)
+
+        with patch.dict(sys.modules, {"pytesseract": mock_pytesseract}):
+            with patch("app.services.ocr_service.Image") as mock_pil:
+                mock_pil.open.return_value = mock_img
+                result = ocr_image("/fake/path.png", lang="zzzz")
+
+        assert result["lang"] == "eng"
+
+
+class TestPdfEditorService:
+    def test_no_edits_raises(self):
+        """Should raise PDFEditorError when no edits provided."""
+        from app.services.pdf_editor_service import apply_pdf_edits, PDFEditorError
+        with pytest.raises(PDFEditorError, match="No edits"):
+            apply_pdf_edits("/fake.pdf", "/out.pdf", [])