Add per-feed visibility settings panel

Visitors can hide individual feeds via a gear-icon panel in the header.
Preferences live in localStorage; the server ships the full source list
(name + channel) as window.PETE_SOURCES so the panel lists every feed,
grouped by channel, regardless of what's on the current page.

internal/web/handlers.go

@@ -43,11 +43,12 @@ func toView(s storage.Story) StoryView {
 }
 
 type pageData struct {
-	SiteTitle string
-	Channels  []Channel
-	Active    string // slug of active channel, "" for landing
-	Weather   Weather
-	Phase     string // when set, forces day/dawn/dusk/night and disables the clock-driven phase JS
+	SiteTitle  string
+	Channels   []Channel
+	Active     string // slug of active channel, "" for landing
+	Weather    Weather
+	Phase      string // when set, forces day/dawn/dusk/night and disables the clock-driven phase JS
+	AllSources template.JS // JSON array of {name, channel} for the settings panel
 }
 
 type channelPage struct {
@@ -78,10 +79,15 @@ type channelStat struct {
 }
 
 func (s *Server) base() pageData {
+	srcJSON, err := json.Marshal(s.sources)
+	if err != nil {
+		srcJSON = []byte("[]")
+	}
 	return pageData{
-		SiteTitle: s.cfg.SiteTitle,
-		Channels:  channels,
-		Weather:   currentWeather(time.Now()),
+		SiteTitle:  s.cfg.SiteTitle,
+		Channels:   channels,
+		Weather:    currentWeather(time.Now()),
+		AllSources: template.JS(srcJSON),
 	}
 }