Add UV index information throughout the app

[Copilot]

UV index data was absent from the app despite being readily available from the existing open-meteo weather API. This PR surfaces UV levels wherever contextually appropriate: current conditions, hourly forecasts, charts, AI recommendations, alert tips, and push notifications.

API

• All weather API calls now request uv_index in current/hourly and uv_index_max in daily parameters

UI (index.html, home.html, home.js)

• Current weather widget: new #current-uv element shows live UV index (or daily max for non-today days)
• Hourly table: new UV Index column with color-coded level badges
• Weather chart: new ☀️ UV Index checkbox adds an optional line dataset on a dedicated y2 right axis
• getUVLevel(uvIndex) helper renders color-coded badges: Low (0–2) → Moderate (3–5) → High (6–7) → Very High (8–10) → Extreme (11+)

Recommendations & alerts (views.py, static-sentiment.js)

• make_recommendation() / makeRecommendation() append UV-specific advice when UV ≥ 6
• get_alert_level() / getAlertLevel() accept weather_data and conditionally append a UV Protection tip to every alert level's tips list
• Static form handler now fetches weather (with UV) in parallel with pollen data via Promise.all

Notifications (send_notifications.py)

• New get_uv_forecast() fetches today's uv_index_max; create_notification_message() includes UV level label and tailored advice in the message body

Translations (translations.js)

• Added EN + RO entries for UV Index, Moderate, Very High, Extreme, UV Protection

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.