fix: replace LL with MM

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This pull request standardizes the date format handling across the backend and frontend by switching from using LL (month) with slashes to the more conventional MM for months. It updates the allowed date formats and default values to ensure consistency and compatibility throughout the application.

Date format standardization:

• Updated the default dateFormat in the Company model from 'dd/LL/yyyy' to 'dd/MM/yyyy' in schema.prisma, ensuring the default uses the conventional month notation.
• Updated the allowed date formats in both the frontend (company.settings.tsx) and backend (date.ts) to use 'MM' instead of 'LL' for months, and replaced formats accordingly. [1] [2]
• Changed the fallback date format in the backend date formatting utility from 'dd/LL/yyyy' to 'dd/MM/yyyy' to match the new standard.