feat: Added validation for max dosage and corresponding test cases #2383

[himanshu-sharmav]

Fixes: #2383

• Added validation to ensure max dosage is greater than or equal to base dosage in PrescriptionSerializer.
• Added test cases to validate the new dosage constraints.
• Updated test_prescriptions_api.py to include tests for valid, equal, and invalid dosage scenarios.

Resolves issue with incorrect dosage validation.

Merge Checklist

• [ X] Tests added/fixed
• [ X] Update docs in /docs
• [ X] Linting Complete
• [ X] Any other necessary step

Only PR's with test cases included and passing lint and test pipelines will be reviewed

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