feat: add PaddleOCR-vl loader support and implement retrieval router infrastructure (#23945)

Co-authored-by: Tim Baek <tim@openwebui.com>
Co-authored-by: joaoback <156559121+joaoback@users.noreply.github.com>

backend/open_webui/config.py

@@ -2827,6 +2827,18 @@ MISTRAL_OCR_API_KEY = PersistentConfig(
     os.getenv('MISTRAL_OCR_API_KEY', ''),
 )
 
+PADDLEOCR_VL_BASE_URL = PersistentConfig(
+    'PADDLEOCR_VL_BASE_URL',
+    'rag.paddleocr_vl_base_url',
+    os.getenv('PADDLEOCR_VL_BASE_URL', 'http://localhost:8080'),
+)
+
+PADDLEOCR_VL_TOKEN = PersistentConfig(
+    'PADDLEOCR_VL_TOKEN',
+    'rag.paddleocr_vl_token',
+    os.getenv('PADDLEOCR_VL_TOKEN', ''),
+)
+
 BYPASS_EMBEDDING_AND_RETRIEVAL = PersistentConfig(
     'BYPASS_EMBEDDING_AND_RETRIEVAL',
     'rag.bypass_embedding_and_retrieval',