Refactor: Rename 'customer' to 'citizen' and translate German terms to English in waiting statistics

[coderabbitai]

Description

This PR introduces new customer type constants and methods in the waiting statistics module that use mixed German/English terminology and the term 'customer' which is inconsistent with the civic domain of this e-appointment system.

Changes Needed

1. Rename 'customer' to 'citizen'

The project uses 'citizen' terminology throughout (zmscitizenapi, zmscitizenview), but the new statistics code uses 'customer'. These should be aligned:

In zmsstatistic/src/Zmsstatistic/Download/WaitingReport.php:

• Rename constants:
  • CUSTOMER_TYPE_GESAMT → CITIZEN_TYPE_TOTAL
  • CUSTOMER_TYPE_TERMIN → CITIZEN_TYPE_SCHEDULED
  • CUSTOMER_TYPE_SPONTAN → CITIZEN_TYPE_WALK_IN
• Rename method: assertValidCustomerType() → assertValidCitizenType()
• Rename method: getCustomerTypeKeys() → getCitizenTypeKeys()
• Update parameter names: $customerType → $citizenType

2. Translate German string values to English

The constant values use German terms which reduces international maintainability:

• 'gesamt' → 'total'
• 'termin' → 'scheduled'
• 'spontan' → 'walkin'

Files to update:

• zmsstatistic/src/Zmsstatistic/Download/WaitingReport.php (constant values, method logic)
• zmsstatistic/src/Zmsstatistic/Helper/ReportHelper.php (if referencing these values)
• zmsdb/src/Zmsdb/Query/ExchangeWaitingscope.php (suffix logic)
• zmsdb/src/Zmsdb/Helper/CalculateDailyWaitingStatisticByCron.php (type determination)
• Any test files referencing these values

Context

Related to PR #1813 which introduced the new total customer statistics functionality.

Backlinks:

• PR: feat(ZMSKVR-1123): new table for total number of customers in waiting statistics #1813

Requested by: @ThomasAFink

Priority

Low - This is a code quality/consistency improvement that can be addressed in a future PR.