Add Nudge to Productivity

[astraedus]

Adds Nudge under Productivity.

Nudge is a privacy-first, open-source app blocker for Android (delay-to-open, reel/click counters, per-app time budgets, breathing exercise, block YouTube Shorts).

It meets the inclusion criteria:

• Licensed FOSS (GPL-3.0), source available on GitHub
• Keeps privacy, no ads, no spyware, and zero internet permission (it literally cannot phone home)
• No proprietary elements
• Stable and actively maintained
• Documentation available (README + project website)
• Free of charge

Linked as project-page-only per the contributing format (not yet on F-Droid/IzzyOnDroid; no Play Store link included, per guidelines).

[offa]

Thanks for your submission and work!
The F-Droid submission seems to have stalled (though no blocker here).