Add commitment templates and presets to the create wizard select-type step

[greatest0fallt1me]

Fixes #951

Summary

• Adds a CommitmentPreset type and COMMITMENT_PRESETS array in src/components/create/commitmentPresets.ts with three named presets (Conservative 90-day, Balanced 60-day, Aggressive 30-day)
• Adds a keyboard-accessible preset picker (role="radiogroup" / role="radio") above the existing type cards in CreateCommitmentStepSelectType
• Wires onApplyPreset callback in src/app/create/page.tsx to prefill durationDays and maxLossPercent state; all fields remain editable in the configure step
• Adds tests in src/components/create/CreateTemplates.test.tsx covering rendering, interaction, keyboard activation, accessibility, scratch option, and data validity
• Adds docs/CREATE_TEMPLATES.md documenting props, behavior, accessibility, and usage examples

Test plan

• Preset buttons render and show labels/descriptions
• Clicking a preset sets aria-checked=true on that preset and aria-checked=false on others
• Configure step opens pre-populated with preset values after selecting a preset
• All configure fields remain editable after preset prefill
• Start from scratch option does not prefill any values
• Keyboard: Enter and Space activate a preset
• Continue button is disabled until a type is selected (either via preset or direct card click)
• Draft persistence saves preset-prefilled values correctly

🤖 Generated with Claude Code

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