Auto-Save a Form with Debounce

My [app] has a form (or text editor) where I want to auto-save the user's work as they type, but without flooding the server with save requests on every keystroke.

Set up a debounced auto-save that:
- Saves automatically [1 second / 2 seconds] after the user stops editing
- Shows a "Saving..." indicator while the save is in progress
- Shows "Saved ✓" when the server confirms
- If the user keeps typing, resets the timer (doesn't save mid-sentence)
- Handles save failures with a retry and a visible warning
- Saves immediately when the user navigates away (don't lose work)

My stack: [your framework and language here]

I'm learning, so explain each part simply.