Add Merchant Settlement History report and view

[Copilot]

Adds historical settlement visibility per merchant to support queries and statement generation.

Changes

Data Model

• MerchantSettlementHistoryModel with settlement date, unique reference, transaction count, and net amount paid
• GetMerchantSettlementHistoryQuery supporting estate, merchant, and date range filters

Mock Data Service

• Generates weekly settlements with unique references: STL-{yyyyMMdd}-{merchant}-{counter}
• Transaction counts (50-500), fee calculations (1.5-2.5%), net amounts (gross - fees)
• Reconciles with existing LastSettlementModel calculation pattern

UI Components

• /reporting/merchant-settlement-history - Standalone report with merchant filter, date range, summary cards, and tabular view
• Settlement History tab in /merchants/{id} view - Shows last 10 settlements with link to full report
• Navigation link in reporting dashboard under Settlement Reporting section

// Settlement reference generation ensures uniqueness
var settlementRef = $"STL-{currentDate:yyyyMMdd}-{merchant.MerchantReference ?? merchant.MerchantId.ToString().Substring(0, 8)}-{settlementCounter:D4}";
// Example: STL-20260108-MERCHANT01-0001

// Net amount calculation compatible with settlement summary
var netAmount = grossAmount - fees;

Data Reconciliation

Settlement history uses consistent calculation with settlement summary reports:

• Net/Settlement Amount = Gross Amount - Fees
• Fee percentages and transaction patterns align with existing TodaysSettlementModel and LastSettlementModel

Original prompt

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This section details on the original issue you should resolve

<issue_title>Issue: Merchant Settlement History</issue_title>
<issue_description>Description: Provide historical settlement visibility per merchant.
Business Value: Supports merchant queries and statement generation.

Data Requirements

• Settlement date
• Settlement reference
• Transaction count
• Net amount paid

Acceptance Criteria

• Settlement references are unique.
• Totals reconcile with Settlement Summary Report.
  </issue_description>

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

• Fixes Issue: Merchant Settlement History #562

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