Update all LangChain and transformers ecosystem dependencies to their
latest major versions with Python 3.10+ support.

## Breaking Changes
- Minimum Python version: 3.9 → 3.10

## LangChain Updates (to v1.x/v3.x/v4.x)
- langchain: 0.3.8 → 1.2.0
- langchain-core: 0.3.29 → 1.2.6
- langchain-openai: 0.2.9 → 1.1.6
- langchain-anthropic: 0.3.0 → 1.3.0
- langchain-google-genai: 2.1.2 → 4.1.2
- langchain-ollama: 0.2.0 → 1.0.1
- langchain-groq: 0.2.1 → 1.1.1
- langchain-mistralai: 0.2.1 → 1.1.1
- langchain-deepseek: 0.1.3 → 1.0.1
- langchain-google-vertexai: 2.0.24 → 3.2.0

## Transformers Ecosystem Updates
- transformers: 4.40.0 → 4.57.3
- torch: 2.2.2 → 2.9.1
- tokenizers: 0.15.2 → 0.22.1
- sentence-transformers: 2.2.0 → 5.2.0
- scikit-learn: 1.3.0 → 1.7.2
- numpy: 1.21.0 → 2.2.6
- accelerate: 1.8.1 → 1.12.0

## Code Changes
- Updated LangChain imports from deprecated paths
  (langchain.schema → langchain_core.documents)
- Added google_api_key parameter to Google LangChain conversion
  (required by langchain-google-genai 4.x)
- Updated tests to match new LangChain behavior

## Test Results
✅ 642 passed, 1 skipped, 0 failures