Router changes for saved filters API:
- Add CreateFilterHTML handler to return HTML for HTMX requests
- Extract CreateFilterHTML function to handle filter creation logic
- Add wrapper for POST /api/saved-filters to detect HTMX requests
- HTMX requests: Return HTML via CreateFilterHTML
- Regular requests: Return JSON via existing handler
- Add collectFilterFormData helper to gather form data from #filter-form
- Improve error handling for duplicate filter names (409 Conflict)
- HTML responses include error messages for better UX
This enables the save filter modal to work without page refresh,
providing a smoother user experience with immediate visual feedback.
john-okeefe
d399a110ca