Replace plain-text city input with geocoding search that resolves
lat/lon coordinates for accurate OpenWeatherMap queries. Users can
now search, see multiple results with state/country detail, and
select the exact location.
- Add GET /api/weather/search endpoint (OWM Geocoding API)
- Add weather_lat/weather_lon columns to settings model + migration
- Use lat/lon for weather API calls when available, fall back to city name
- Replace settings text input with debounced search + dropdown selector
- Show selected location as chip with clear button
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>