feat: add breathing technique presets

[0then0]

• Adds four presets to the existing technique catalogue:
  • 1-4-2 Ratio (5-20-10-0)
  • Advanced 5-7-9 (5-7-9-0)
  • Rectangular (5-8-5-8)
  • Wim Hof Method (2-0-2-0)
• Uses the current PatternPreset structure without introducing an unused color field.
• Documents that the Wim Hof preset covers the active breathing phase only; retention rounds need a separate exercise-engine feature.
• Keeps stable preset IDs for persisted settings compatibility.
• Adds tests for the exact new patterns and duplicate IDs.

Closes #80