feat: add date range filter to dashboard and anti-patterns pages

[kumaresan-subramani]

Description

Adds date range filtering to the Dashboard and Anti-Patterns pages, allowing users to focus analysis on specific time periods (Last 7/28/90/180 days or all-time data).

Changes

• Add activeRangeDays module-level state to track selected date range
• Implement buildRangeFilter() helper function that dynamically calculates fromDate based on selected range
• Update all RPC calls in Dashboard page (getStats, getDailyActivity, getWorkspaceBreakdown, getHarnessBreakdown, getAntiPatterns, getCodeProduction) to use filtered date range
• Update all RPC calls in Anti-Patterns page (getAntiPatterns, getRuleEditor) to use filtered date range
• Add 5 preset date range buttons to both pages (Last 7 days, Last 4 weeks, Last 3 months, Last 6 months, All time)
• Wire event listeners for instant re-rendering when date range changes
• Pass filtered context to rule editor so rule testing respects selected date range
• Use existing .cons-range-bar and .cons-range-btn CSS classes (no new styles needed)

User Experience

• Users can now click date range buttons to quickly filter data
• Selected range persists across tab/page navigation
• Rule testing in editor respects the selected date range
• Active button styling shows current selection

Related Issues

Checklist

• npm run check passes (typecheck + lint + spellcheck + knip + tests)
• Changes are covered by tests (if applicable)
• Documentation updated (if applicable)

final output

[kumaresan-subramani]

@microsoft-github-policy-service agree

issue - #174