Implement time-based filters

[RossCabrera]

Overview

Add time-based filtering to show notes created/updated within Today,
Last 7 Days (Week), or Last 30 Days (Month) without page refresh.

Requirements

• Create filter buttons: Today, Week, Month, All
• Filter notes client-side based on timestamps
• Show active filter state
• Update notes list instantly
• Work in combination with category filters

Implementation

• Calculate date ranges (Today = 24hrs ago, Week = 7 days, etc.)
• Filter useNotes() data client-side
• Combine with category filter
• No additional API calls needed

UI

• Tab-style buttons or dropdown
• Show active filter
• Display count of filtered notes
• Reset to All option

Acceptance Criteria

• Today filter shows last 24 hours (AC-NAV-01)
• Week filter shows last 7 days (AC-NAV-01)
• Month filter shows last 30 days (AC-NAV-01)
• Filters use updated_at timestamp (AC-NAV-01)
• UI updates instantly (AC-NAV-02)
• Works with category filter
• Active filter highlighted
• Works on all devices

Related User Stories

• US-NAV-07: Time-based filtering

Related Acceptance Criteria

• AC-NAV-01: Filters use created_at/updated_at
• AC-NAV-02: UI updates instantly

Related Issues

• Depends on: Build note grid/card view #23
• Blocks: Add error toast notifications #28