feat: add comprehensive test suite and input validation#1

8harath wants to merge 1 commit intoINDIAPOST-gov:mainINDIAPOST-gov/digipin:mainfrom

8harath:claude/add-useful-feature-01UVyUsojHneTQZDT4VSjVFG8harath/digi-pin:claude/add-useful-feature-01UVyUsojHneTQZDT4VSjVFGCopy head branch name to clipboard