Rework my old app

[dephizee]

A minor issue

[pvium-bounty-app]

Pvium bounty registered for #1.

Reward: 5 USDC

A merged PR that closes this issue can be processed for payment.

[Zhenvip]

Submitted PR #2 for this bounty: #2

It hardens the public image serving path, adds focused regression tests, and closes this issue when merged.

[Finesssee]

Submitted PR #4 for the 5 USDC Pvium bounty: #4

It reworks app configuration, hardens public image serving, validates form/upload inputs, adds upload filename safety, and includes regression tests. The PR uses Closes #1 so it can be processed on merge.