feat: support remote storage for context store

[beinan]

Summary

• add a generic ContextStoreOptions that threads Lance storage options through open/create
• surface storage_options via the PyO3 binding and Python facade with optional AWS overrides
• cover S3-backed persistence with moto-based tests and document remote usage

Testing

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• cargo build -p lance-context-python --release
• python/.venv/bin/pytest python/tests/test_persistence.py
• python/.venv/bin/ruff check python/
• python/.venv/bin/pyright -p python/pyproject.toml