Build a single-page app that helps plant lovers track when each of their potted plants needs watering.

The user can **add plants** by typing a name (e.g. "Monstera") and selecting a watering frequency in days (e.g. every 3 days, every 7 days). Each plant appears as a card that shows:
- The plant's name
- How many days until the next watering (counting down from the last-watered date)
- A **"Water Now"** button that resets the countdown to zero and restarts the timer from today
- A **delete** button to remove the plant

When a plant is overdue (countdown hits 0 or below), its card should visually alert the user — for example by turning the card border red or showing a wilted emoji 🥀.

All plant data must persist in `localStorage` so refreshing the page doesn't wipe the list. There is no login, no backend, and no external API — just a clean, functional widget a forgetful plant parent would actually use.