feat: configurable CLI tool for generating Stommel diagrams from Google Sheets

[madsCodeBuddy]

Goal

A CLI tool so users can generate Stommel diagrams from a Google Sheet ID without writing Python:

timespace --sheet-id 1abc123 --output stommel.html
timespace --csv data.csv --output stommel.html

Scope

• Accept Google Sheet ID or local CSV path
• Support space_on_x=True/False flag
• Output static HTML (default) or open in browser
• Use existing extract_google_sheet + transform_* + create_space_time_figure pipeline

Migrated from timeSpace-private #131