feat(GPT-30): amplify create new item implementation

[devkobetran]

• GPT-30
• Developer Notes
• Implemented AWS Amplify Backend create new item
• Moved UI code to create new item page
• created isSafeUrl helper function to check if url is safe
• use vite test to run test cases
• this PR is intermediate step. to thoroughly test if the code works, need to implement create new store first and test the two together.
• @jecheung9 , you don't need to learn thoroughly every detail of this PR just yet. Wait until part 2 is implemented and everything is thoroughly tested before looking at the code to learn from it.

UI changes: