Add filtering and pagination to merchant list

[Copilot]

Merchant list lacked ability to filter by key fields or navigate large datasets. Added 5 filters (name, reference, settlement schedule, region, postcode) and pagination with configurable page size.

Changes

UI Enhancements

• Added filter controls in responsive 5-column grid
• Added Region and Postcode columns to merchant table
• Added pagination controls (First/Previous/Next/Last) with result count display
• Added configurable page size selector (5, 10, 25, 50 items per page)
• Summary cards now reflect filtered results

Backend

• Expanded mock merchant data from 3 to 12 entries with Region/PostalCode populated
• Added unit tests for filter UI, pagination display, and new columns

Performance

• Single-pass LINQ filtering with compound predicate instead of chained Where clauses
• Cached filtered/paged results and totalPages to avoid recomputation
• Filters trigger on blur/change rather than per-keystroke
• Auto-reset pagination to page 1 when filters or page size changes

// Combined filtering in single pass
_filteredMerchants = allMerchants.Where(m =>
    (string.IsNullOrWhiteSpace(_filterName) || 
     (m.MerchantName?.Contains(_filterName, StringComparison.OrdinalIgnoreCase) ?? false)) &&
    (string.IsNullOrWhiteSpace(_filterReference) || 
     (m.MerchantReference?.Contains(_filterReference, StringComparison.OrdinalIgnoreCase) ?? false)) &&
    // ... other filters
).ToList();

All filters work independently and in combination. Clear Filters button resets all state. Users can adjust the number of items displayed per page using the page size selector (default: 10 items).

> [!WARNING]
>
>

Original prompt

>
> ----
>
> This section details on the original issue you should resolve
>
> <filter_complete></filter_complete>

<issue_title>Merchant List needs new filters</issue_title>
><issue_description>Reference
> Name
> Settlement Schedule
> Region
> Postcode
>
> Add in paging as well to the list</issue_description>
>
> ## Comments on the Issue (you are @copilot in this section)
>
>
>

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Merchant List needs new filters</issue_title>
<issue_description>Reference
Name
Settlement Schedule
Region
Postcode

Add in paging as well to the list</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Merchant List needs new filters #657

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[StuartFerguson]

@copilot can you make the pagination changeable maybe 5,10,25,50

[Copilot]

@copilot can you make the pagination changeable maybe 5,10,25,50

Done! Added a page size selector with options for 5, 10, 25, and 50 items per page. The selector is integrated into the pagination controls on the left side. When the page size changes, the list automatically resets to page 1 and recalculates the pagination. The pagination controls are now visible even when there's only one page, so users can always change the page size.

Commit: 91345f4