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/app/routes/pdf_editor.py

@@ -0,0 +1,80 @@
+"""PDF Editor route — apply text annotations to PDFs."""
+import json
+
+from flask import Blueprint, request, jsonify, current_app
+
+from app.extensions import limiter
+from app.services.policy_service import (
+    assert_quota_available,
+    build_task_tracking_kwargs,
+    PolicyError,
+    record_accepted_usage,
+    resolve_web_actor,
+    validate_actor_file,
+)
+from app.utils.file_validator import FileValidationError
+from app.utils.sanitizer import generate_safe_path
+from app.tasks.pdf_editor_tasks import edit_pdf_task
+
+pdf_editor_bp = Blueprint("pdf_editor", __name__)
+
+
+@pdf_editor_bp.route("/edit", methods=["POST"])
+@limiter.limit("10/minute")
+def edit_pdf_route():
+    """Apply text annotations to a PDF.
+
+    Accepts: multipart/form-data with:
+        - 'file': PDF file
+        - 'edits': JSON string — array of edit objects
+          Each edit: { type: "text", page: 1, x: 100, y: 200, content: "Hello", fontSize: 14, color: "#000000" }
+    Returns: JSON with task_id for polling
+    """
+    if not current_app.config.get("FEATURE_EDITOR", False):
+        return jsonify({"error": "This feature is not enabled."}), 403
+
+    if "file" not in request.files:
+        return jsonify({"error": "No file provided."}), 400
+
+    file = request.files["file"]
+    edits_raw = request.form.get("edits", "[]")
+
+    try:
+        edits = json.loads(edits_raw)
+        if not isinstance(edits, list):
+            return jsonify({"error": "Edits must be a JSON array."}), 400
+    except (json.JSONDecodeError, TypeError):
+        return jsonify({"error": "Invalid JSON in 'edits' field."}), 400
+
+    if not edits:
+        return jsonify({"error": "At least one edit is required."}), 400
+
+    if len(edits) > 500:
+        return jsonify({"error": "Maximum 500 edits allowed."}), 400
+
+    actor = resolve_web_actor()
+    try:
+        assert_quota_available(actor)
+    except PolicyError as e:
+        return jsonify({"error": e.message}), e.status_code
+
+    try:
+        original_filename, ext = validate_actor_file(
+            file, allowed_types=["pdf"], actor=actor
+        )
+    except FileValidationError as e:
+        return jsonify({"error": e.message}), e.code
+
+    task_id, input_path = generate_safe_path(ext, folder_type="upload")
+    file.save(input_path)
+
+    task = edit_pdf_task.delay(
+        input_path, task_id, original_filename, edits,
+        **build_task_tracking_kwargs(actor),
+    )
+    record_accepted_usage(actor, "pdf-edit", task.id)
+
+    return jsonify({
+        "task_id": task.id,
+        "message": "PDF editing started. Poll /api/tasks/{task_id}/status for progress.",
+    }), 202