feat: add Ragcon provider (#13425)

### What problem does this PR solve?

This PR aims to extend the list of possible providers. Adds new Provider
"RAGcon" within the Ollama Modal. It provides all model types except OCR
via Openai-compatible endpoints.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Jakob <16180662+hauberj@users.noreply.github.com>

rag/llm/embedding_model.py

@@ -1080,3 +1080,17 @@ class JiekouAIEmbed(OpenAIEmbed):
         if not base_url:
             base_url = "https://api.jiekou.ai/openai/v1/embeddings"
         super().__init__(key, model_name, base_url)
+
+class RAGconEmbed(OpenAIEmbed):
+    """
+    RAGcon Embedding Provider - routes through LiteLLM proxy
+    
+    Default Base URL: https://connect.ragcon.ai/v1
+    """
+    _FACTORY_NAME = "RAGcon"
+    
+    def __init__(self, key, model_name="text-embedding-3-small", base_url=None):
+        if not base_url:
+            base_url = "https://connect.ragcon.com/v1"
+        
+        super().__init__(key, model_name, base_url)