Define explicit expected values in filter variable replacement tests

[Rello]

Motivation

• Make testReplaceFilterVariables deterministic by defining expected options and values per case instead of deriving them via reflection.
• Improve clarity of test cases for multiple %...% filter patterns and formats.
• Avoid depending on private method invocations in tests by calculating expected timestamps locally.

Description

• Replace reflection-based parsing in tests/Service/VariableServiceTest.php with a data provider replaceFilterVariablesProvider that supplies explicit expected options and values.
• Add local helper methods expectedStartTimestamp and expectedQuarterRange to compute expected timestamps and quarter ranges for provider cases.
• Update testReplaceFilterVariables signature to accept the expected option and expected value and assert the service output against those values.
• Add a one-line entry to CHANGELOG.md documenting the extended filter variable replacement tests.

Testing

• No automated tests were executed as part of this change.
• The modified test file is tests/Service/VariableServiceTest.php and can be run with vendor/bin/phpunit tests/Service/VariableServiceTest.php if desired.

---

Codex Task