Add Ollama embedding support to enable local embedding models (#22)

* feat: Add Ollama embedding support for local embedding models

* docs: Add clear documentation for Ollama embedding usage

* feat: Enhance Ollama embedding with better error handling and concurrent processing

- Add intelligent model validation and suggestions (inspired by OllamaChat)
- Implement concurrent processing for better performance
- Add retry mechanism with timeout handling
- Provide user-friendly error messages with emojis
- Auto-detect and recommend embedding models
- Add text truncation for long texts
- Improve progress bar display logic

* docs: don't mention it in README

apps/base_rag_example.py

@@ -75,7 +75,7 @@ class BaseRAGExample(ABC):
             "--embedding-mode",
             type=str,
             default="sentence-transformers",
-            choices=["sentence-transformers", "openai", "mlx"],
+            choices=["sentence-transformers", "openai", "mlx", "ollama"],
             help="Embedding backend mode (default: sentence-transformers)",
         )
 
@@ -85,7 +85,7 @@ class BaseRAGExample(ABC):
             "--llm",
             type=str,
             default="openai",
-            choices=["openai", "ollama", "hf"],
+            choices=["openai", "ollama", "hf", "simulated"],
             help="LLM backend to use (default: openai)",
         )
         llm_group.add_argument(