Fixed monthly recurring tasks off by one

[Tanmay-Nalawade]

[//]: Fixes #15496

Changes

• Original code assumed months start on the 1st and are occurring at 7-day blocks, causing weekday calculations to sometimes shift dates.
• Removed weekday calculation depending on the current week.
• Now it calculates the nth weekday of the month by anchoring to the start of the month hence removing additional logic checks.
• Added a max iteration limit of 48 (4 years) to prevent a potential infinite loop in edge cases.

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