Desktop License Key Manager

PLEASE READ THIS !!!!!
(if you can not stay within my budget please dont write me i am not going over my budget )

I need a small, self-contained application that lets me create and validate license keys for my Windows desktop software. The workflow is intentionally simple: I type or paste a new key, hit “Save,” and the tool stores it securely; my main application can then call a validation routine (or a lightweight API) to check any key a user enters.

Core requirements
• Manual entry screen for new keys, with basic field validation to avoid duplicates.
• Fast, reliable validation method that I can embed or call from my desktop app.
• Secure storage of all keys—file-based, SQLite, or another light local database is fine as long as keys are encrypted at rest.
• Clean, minimal UI built with any modern stack you’re comfortable with (C#, WPF, Electron, Python + Tkinter/PySide—your choice, as long as deployment is straightforward).
• Full source code and concise setup/integration notes so I can plug the validator into my existing codebase quickly.

No usage tracking or user account features are needed; the focus is strictly on manual key creation and on-demand validation. If you’ve built similar licensing tools or have a preferred encryption approach, tell me about it in your bid.

(if you can not stay within my budget please dont write me i am not going over my budget )