fix(mypy): resolve typing issues in post-training providers and model files

This commit achieves zero mypy errors across all 430 source files by addressing type issues in post-training providers, model implementations, and testing infrastructure.

Key changes:
- Created HFAutoModel Protocol for HuggingFace models to provide type safety without requiring complete type stubs
- Added module overrides in pyproject.toml for libraries lacking type stubs (torchtune, fairscale, torchvision, datasets, etc.)
- Fixed type issues in databricks provider and api_recorder

Using centralized mypy.overrides instead of scattered inline suppressions provides cleaner code organization.

pyproject.toml

@@ -347,7 +347,17 @@ exclude = [
 
 [[tool.mypy.overrides]]
 # packages that lack typing annotations, do not have stubs, or are unavailable.
-module = ["yaml", "fire"]
+module = [
+    "yaml",
+    "fire",
+    "torchtune.*",
+    "fairscale.*",
+    "torchvision.*",
+    "datasets",
+    "nest_asyncio",
+    "streamlit_option_menu",
+    "lmformatenforcer.*",
+]
 ignore_missing_imports = true
 
 [tool.pydantic-mypy]