Add pact templates for common commitments

[vayungodara]

Problem

Users must create every pact from scratch. This adds friction, especially for common commitment types like exercise, reading, or study goals.

What to change

• Create a set of default pact templates (e.g. "Exercise 3x/week", "Read 20 min/day", "No social media before noon")
• Add a template picker to the pact creation flow
• Templates should pre-fill title, description, frequency, and suggested check-in schedule
• Allow users to customize after selecting a template

Acceptance criteria

• At least 5 default templates available
• Template picker accessible from pact creation
• Selecting a template pre-fills the form
• Users can edit all pre-filled fields

Label: feature
Priority: medium

[vayungodara]

Closed by PR #26 — pact templates with 20 presets across 5 categories, two-step creation flow, monthly recurrence added.