feat: add OWM alerts, UV index support, and provider info UI

- Parse OWM One Call 3.0 weather alerts and map to Warning structs
- Map hourly UVI from OWM response to HourlyForecast.UVIndex
- Add severity helper mapping OWM alert tags to severity levels
- Extract UVIndex through compute layer to timeline slots
- Smart warnings: use provider-supplied alerts, fall back to DWD
- Show UV index in dashboard timeline tooltips
- Add provider description below forecast dropdown with i18n

internal/compute/compute.go

@@ -122,6 +122,7 @@ func BuildDashboard(req ComputeRequest) (DashboardData, error) {
 		cloudPct := 50.0
 		sunMin := 0.0
 		pressureHpa := 0.0
+		uvIndex := 0.0
 		if i < len(dayForecasts) {
 			if dayForecasts[i].CloudCoverPct != nil {
 				cloudPct = *dayForecasts[i].CloudCoverPct
@@ -132,6 +133,9 @@ func BuildDashboard(req ComputeRequest) (DashboardData, error) {
 			if dayForecasts[i].PressureHpa != nil {
 				pressureHpa = *dayForecasts[i].PressureHpa
 			}
+			if dayForecasts[i].UVIndex != nil {
+				uvIndex = *dayForecasts[i].UVIndex
+			}
 		}
 
 		budgets, worstStatus, worstMode := computeRoomBudgets(req, h.Hour, h.TempC, cloudPct, sunMin, toggles)
@@ -144,6 +148,7 @@ func BuildDashboard(req ComputeRequest) (DashboardData, error) {
 			TempC:        h.TempC,
 			HumidityPct:  h.HumidityPct,
 			PressureHpa:  pressureHpa,
+			UVIndex:      uvIndex,
 			RiskLevel:    dayRisk.Level.String(),
 			BudgetStatus: worstStatus.String(),
 			IndoorTempC:  indoorTempC,

internal/compute/compute_test.go

@@ -30,6 +30,17 @@ func makeForecasts(baseTime time.Time, temps []float64) []Forecast {
 	return forecasts
 }
 
+func makeForecastsWithUVI(baseTime time.Time, temps []float64, uvis []float64) []Forecast {
+	forecasts := makeForecasts(baseTime, temps)
+	for i := range forecasts {
+		if i < len(uvis) {
+			uv := uvis[i]
+			forecasts[i].UVIndex = &uv
+		}
+	}
+	return forecasts
+}
+
 func TestBuildDashboard_NoForecasts(t *testing.T) {
 	req := ComputeRequest{
 		Profile: Profile{Name: "Test", Timezone: "Europe/Berlin"},
@@ -850,3 +861,40 @@ func TestBuildDashboard_MultipleRooms(t *testing.T) {
 		t.Errorf("got %d room budgets, want 2", len(data.RoomBudgets))
 	}
 }
+
+func TestBuildDashboard_UVIndex(t *testing.T) {
+	loc, _ := time.LoadLocation("UTC")
+	base := time.Date(2025, 7, 15, 0, 0, 0, 0, loc)
+
+	temps := make([]float64, 24)
+	uvis := make([]float64, 24)
+	for i := range temps {
+		temps[i] = 30
+		if i >= 10 && i <= 14 {
+			uvis[i] = 8.5
+		}
+	}
+
+	req := ComputeRequest{
+		Profile:   Profile{Name: "Test", Timezone: "UTC"},
+		Forecasts: makeForecastsWithUVI(base, temps, uvis),
+		Toggles:   map[string]bool{},
+		Date:      "2025-07-15",
+	}
+
+	data, err := BuildDashboard(req)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(data.Timeline) != 24 {
+		t.Fatalf("got %d timeline slots, want 24", len(data.Timeline))
+	}
+	// Hour 12 should have UVI 8.5
+	if data.Timeline[12].UVIndex != 8.5 {
+		t.Errorf("Timeline[12].UVIndex = %v, want 8.5", data.Timeline[12].UVIndex)
+	}
+	// Hour 0 should have UVI 0
+	if data.Timeline[0].UVIndex != 0 {
+		t.Errorf("Timeline[0].UVIndex = %v, want 0", data.Timeline[0].UVIndex)
+	}
+}

internal/compute/types.go

@@ -99,6 +99,7 @@ type Forecast struct {
 	SunshineMin   *float64  `json:"sunshineMin"`
 	ApparentTempC *float64  `json:"apparentTempC"`
 	PressureHpa   *float64  `json:"pressureHpa"`
+	UVIndex       *float64  `json:"uvIndex"`
 }
 
 // Warning holds a weather warning sent from the client.
@@ -172,6 +173,7 @@ type TimelineSlotData struct {
 	TempC        float64      `json:"tempC"`
 	HumidityPct  float64      `json:"humidityPct"`
 	PressureHpa  float64      `json:"pressureHpa"`
+	UVIndex      float64      `json:"uvIndex"`
 	RiskLevel    string       `json:"riskLevel"`
 	BudgetStatus string       `json:"budgetStatus"`
 	IndoorTempC  float64      `json:"indoorTempC"`