Canvas-based seasonal weather effects + demo page

Server picks variant from Lisbon-local date (rain/petals/jacaranda/motes/leaves)
and renders behind content via a canvas particle layer. Each variant has a
hand-drawn silhouette so shapes are recognizable. /weather demo route exposes
variant + intensity + phase pickers, locking the time-of-day phase override.

internal/web/server.go

@@ -48,7 +48,7 @@ type Server struct {
 // gets its own template set sharing layout.html + _card.html, which avoids
 // `main` define collisions between pages.
 func New(cfg config.WebConfig) (*Server, error) {
-	pages := []string{"index", "channel"}
+	pages := []string{"index", "channel", "weather"}
 	tpls := make(map[string]*template.Template, len(pages))
 	for _, p := range pages {
 		t, err := template.New("").Funcs(funcs).ParseFS(templateFS,
@@ -72,6 +72,7 @@ func New(cfg config.WebConfig) (*Server, error) {
 	mux.HandleFunc("GET /img/{name}", s.handleImg)
 
 	mux.HandleFunc("GET /{$}", s.handleIndex)
+	mux.HandleFunc("GET /weather", s.handleWeatherDemo)
 	for _, ch := range channels {
 		ch := ch
 		mux.HandleFunc("GET /"+ch.Slug, func(w http.ResponseWriter, r *http.Request) {