Add RSVP support and Open Graph meta tags

People can now RSVP without claiming a slot. OG tags show
event title, date/time/location, and headcount in link previews.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

handlers.go

@@ -96,6 +96,7 @@ type SlotView struct {
 type EventPageData struct {
 	Event      db.Event
 	Slots      []SlotView
+	Rsvps      []db.Rsvp
 	TotalGoing int64
 	IsAdmin    bool
 }
@@ -143,9 +144,16 @@ func (s *Server) loadEventPage(r *http.Request, slug string, isAdmin bool) (*Eve
 		})
 	}
 
+	rsvps, err := s.q.ListRsvps(r.Context(), event.ID)
+	if err != nil {
+		return nil, err
+	}
+	totalGoing += int64(len(rsvps))
+
 	return &EventPageData{
 		Event:      event,
 		Slots:      slotViews,
+		Rsvps:      rsvps,
 		TotalGoing: totalGoing,
 		IsAdmin:    isAdmin,
 	}, nil
@@ -262,6 +270,63 @@ func (s *Server) handleUnclaim(w http.ResponseWriter, r *http.Request) {
 	pageTmpl["slots"].ExecuteTemplate(w, "slots-inner", data)
 }
 
+// --- RSVP ---
+
+func (s *Server) handleRsvp(w http.ResponseWriter, r *http.Request) {
+	slug := chi.URLParam(r, "slug")
+	r.ParseForm()
+
+	name := strings.TrimSpace(r.FormValue("name"))
+	if name == "" {
+		http.Error(w, "Name is required", http.StatusBadRequest)
+		return
+	}
+	note := strings.TrimSpace(r.FormValue("note"))
+
+	event, err := s.q.GetEventBySlug(r.Context(), slug)
+	if err != nil {
+		http.Error(w, "Event not found", http.StatusNotFound)
+		return
+	}
+
+	_, err = s.q.CreateRsvp(r.Context(), db.CreateRsvpParams{
+		EventID: event.ID, Name: name, Note: note,
+	})
+	if err != nil {
+		log.Printf("create rsvp: %v", err)
+		http.Error(w, "Failed", http.StatusInternalServerError)
+		return
+	}
+
+	s.notify(slug)
+
+	data, err := s.loadEventPage(r, slug, false)
+	if err != nil {
+		http.Error(w, "error", http.StatusInternalServerError)
+		return
+	}
+	pageTmpl["slots"].ExecuteTemplate(w, "slots-inner", data)
+}
+
+func (s *Server) handleUnrsvp(w http.ResponseWriter, r *http.Request) {
+	slug := chi.URLParam(r, "slug")
+	rsvpID, err := strconv.ParseInt(chi.URLParam(r, "rsvpID"), 10, 64)
+	if err != nil {
+		http.Error(w, "Invalid RSVP", http.StatusBadRequest)
+		return
+	}
+
+	s.q.DeleteRsvp(r.Context(), rsvpID)
+	s.notify(slug)
+
+	data, err := s.loadEventPage(r, slug, false)
+	if err != nil {
+		http.Error(w, "error", http.StatusInternalServerError)
+		return
+	}
+	pageTmpl["slots"].ExecuteTemplate(w, "slots-inner", data)
+}
+
 // --- SSE ---
 
 func (s *Server) handleSSE(w http.ResponseWriter, r *http.Request) {