feat: add support for storing query results to cloud storage

[mpetazzoni]

Summary

Adds support for the store capability from the SQL API, allowing query results to be stored in cloud storage instead of being returned directly over the WebSocket connection.

• Add Store configuration class with for_download() convenience method
• Add StorageFormat enum (parquet, csv, geojson)
• Add StoreResult dataclass to capture the result URI and size
• Add store parameter to cursor.execute()
• Add cursor.get_store_result() method to retrieve store results
• Reorganize internal types and models into dedicated modules (types.py, models.py)

Usage

from wherobots.db import connect, Store, StorageFormat

conn = connect(api_key=api_key, runtime=Runtime.TINY)
cursor = conn.cursor()

# Store results with a presigned URL for download
cursor.execute("SELECT * FROM my_table", store=Store.for_download())
store_result = cursor.get_store_result()
print(f"Results at: {store_result.result_uri} ({store_result.size} bytes)")

# Or with a specific format
cursor.execute("SELECT * FROM my_table", store=Store.for_download(StorageFormat.CSV))

[mpetazzoni]

Replaces #39.