feat: dynamic line stroke settings

webapp/backend/pkg/database/scrutiny_repository_migrations.go

@@ -325,6 +325,12 @@ func (sr *scrutinyRepository) Migrate(ctx context.Context) error {
 						SettingDataType:       "bool",
 						SettingValueBool:      false,
 					},
+					{
+                        SettingKeyName:        "line_stroke",
+                        SettingKeyDescription: "Temperature chart line stroke ('smooth' | 'straight' | 'stepline')",
+                        SettingDataType:       "string",
+                        SettingValueString:    "smooth",
+                    },
 
 					{
 						SettingKeyName:        "metrics.notify_level",

webapp/backend/pkg/models/settings.go

@@ -14,6 +14,7 @@ type Settings struct {
 	DashboardSort    string `json:"dashboard_sort" mapstructure:"dashboard_sort"`
 	TemperatureUnit  string `json:"temperature_unit" mapstructure:"temperature_unit"`
 	FileSizeSIUnits  bool   `json:"file_size_si_units" mapstructure:"file_size_si_units"`
+	LineStroke       string `json:"line_stroke" mapstructure:"line_stroke"`
 
 	Metrics struct {
 		NotifyLevel            int `json:"notify_level" mapstructure:"notify_level"`