Normalize workflows

[mvarrieur]

Summary

• Refactor workflow trigger evaluation into shared triggers.ts logic so maintenance and date-based rules use normalized trigger handling and reusable notification variable builders.
• Add workflow preview helpers to compute “next fire” states for the settings page, including measurement-based previews, cooldown/waiting states, and a fix for same-day calendar occurrences.
• Update workflow UI copy and notification templates to use measurement-neutral wording instead of km-only text, and add coverage for trigger normalization/evaluation plus preview date behavior.

[hawkinslabdev]

Awesome! Thanks again @mvarrieur.