feat(llm): Add Ollama provider and PyMuPDF image extraction

This commit introduces support for Ollama as an alternative Large Language Model (LLM) provider and enhances PDF image extraction capabilities.

- **Ollama Integration:**
    - Implemented `set_ollama_config` to configure Ollama's base URL from `config.ini`.
    - Modified `llm.py` to dynamically select and configure the LLM (Gemini or Ollama) based on the `PROVIDER` setting.
    - Updated `get_model_name` to return provider-specific default model names.
    - `pdf_convertor.py` now conditionally initializes `ChatGoogleGenerativeAI` or `ChatOllama` based on the configured provider.
- **PyMuPDF Image Extraction:**
    - Added a new `extract_images_from_pdf` function using PyMuPDF (`fitz`) for direct image extraction from PDF files.
    - Introduced `get_extract_images_from_pdf_flag` to control this feature via `config.ini`.
    - `convert_pdf_to_markdown` and `refine_content` functions were updated to utilize this new image extraction method when enabled.
- **Refinement Flow:**
    - Adjusted the order of `save_md_images` in `main.py` and added an option to save the refined markdown with a specific filename (`index_refined.md`).
- **Dependencies:**
    - Updated `pyproject.lock` to include new dependencies for Ollama integration (`langchain-ollama`) and PyMuPDF (`PyMuPDF`), along with platform-specific markers for NVIDIA dependencies.

llm.py

@@ -2,6 +2,13 @@ import configparser
 import os
 
 
+def set_api_key(provider: str) -> None:
+    if provider == "gemini":
+        set_gemini_api_key()
+    elif provider == "ollama":
+        set_ollama_config()
+
+
 def set_gemini_api_key() -> None:
     config = configparser.ConfigParser()
     config.read("config.ini")
@@ -17,10 +24,28 @@ def set_gemini_api_key() -> None:
     return
 
 
+def set_ollama_config() -> None:
+    config = configparser.ConfigParser()
+    config.read("config.ini")
+    ollama_base_url = config.get(
+        "llm", "OLLAMA_BASE_URL", fallback="http://localhost:11434"
+    )
+
+    if not os.environ.get("OLLAMA_BASE_URL"):
+        os.environ["OLLAMA_BASE_URL"] = ollama_base_url
+    return
+
+
 def get_model_name() -> str:
     config = configparser.ConfigParser()
     config.read("config.ini")
-    return config.get("llm", "MODEL_NAME", fallback="gemini-2.5-flash")
+    provider = config.get("llm", "PROVIDER", fallback="gemini")
+    if provider == "gemini":
+        return config.get("llm", "MODEL_NAME", fallback="gemini-2.5-flash")
+    elif provider == "ollama":
+        return config.get("llm", "MODEL_NAME", fallback="gemma3:latest")
+    return "gemini-2.5-flash"  # Default fallback
+
 
 def get_temperature() -> float:
     config = configparser.ConfigParser()