What does this PR do?

This PR refactors the insights date filtering system to unify date filtering with the existing column filter system, replacing the previous separate dateRange handling with dynamic column filters based on dateTarget ("startTime" or "createdAt").

Key Changes:

• Replace hardcoded "timestamp" column with dynamic getDateColumn(dateTarget) function
• Update backend to handle "startTime" and "createdAt" as date range column filters
• Remove dateRange, startDate, endDate, and dateTarget from schemas and tRPC procedures
• Extract date ranges from columnFilters instead of separate parameters
• Unify date filtering with the general column filter system

Link to Devin run: https://app.devin.ai/sessions/6095c8602d414a0aabafe2eeaf5af329
Requested by: @eunjae-lee

This PR is stacked on top of #23752.

How should this be tested?

⚠️ Critical: This PR involves significant changes to date filtering logic and requires thorough testing:

1. Date Filter Testing:

   • Test date filtering with both "startTime" and "createdAt" options
   • Verify date range selection works correctly for both targets
   • Test preset date ranges (Last 7 days, Last 30 days, etc.)

2. Previous Period Comparisons:

   • Verify that booking stats show correct previous period comparisons
   • Test that percentage changes are calculated correctly

3. URL State Persistence:

   • Change date ranges and verify URL updates correctly
   • Refresh page and verify filters persist
   • Test browser back/forward navigation

4. CSV Export:

   • Test CSV export functionality with different date ranges
   • Verify filename includes correct dates

5. Charts and Tables:

   • Verify all charts render correctly with filtered data
   • Test that data updates when changing date targets

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox. N/A - Internal refactoring with no user-facing changes.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

Human Review Checklist

⚠️ High Priority Items:

• Test actual date filtering functionality - Verify both startTime and createdAt filtering work correctly with real data
• Validate previous period calculations - Ensure booking stats comparisons still work after refactoring calculatePreviousPeriodDates
• Check type safety - Review type assertions (as ColumnFilter) for potential runtime issues
• Test error handling - Verify graceful handling when date ranges are missing from column filters
• Validate CSV export - Ensure export functionality works with new date extraction logic
• Test URL state persistence - Verify date filters persist correctly in URL and on page refresh

Medium Priority:

• Review schema changes for potential breaking changes to other parts of the system
• Verify all tRPC procedures correctly extract dates from column filters
• Test edge cases like invalid date formats or missing date data

Checklist

• I have read the contributing guide
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have checked if my changes generate no new warnings