Add yes/no RSVP answers with required login

RSVPs now carry a status ('yes'/'no'). When auth is enabled, answering
requires login for all events, not just capped ones. Answers are deduped
one per user and re-answering updates in place. A 'no' zeroes plus_one,
is excluded from Going counts and cap math, frees the person's slot
claims, and shows in a separate "Can't make it" list.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

templates/slots.html

@@ -37,11 +37,11 @@
   {{if .GoingList}}
     {{range .GoingList}}
     <span class="claim-chip">
-      {{if gt .RsvpID 0}}<span class="rsvp-name-link"
+      {{if and (gt .RsvpID 0) $.CanEditRsvps}}<span class="rsvp-name-link"
         hx-get="/e/{{$.Event.Slug}}/rsvp/{{.RsvpID}}/edit"
         hx-target="#edit-modal"
         hx-swap="innerHTML">{{.Name}}</span>{{else}}{{.Name}}{{end}}{{if gt .PlusOne 0}} +{{.PlusOne}}{{end}}{{if .Note}} <small style="color:#888">({{.Note}})</small>{{end}}
-      {{if gt .RsvpID 0}}
+      {{if and (gt .RsvpID 0) $.CanEditRsvps}}
       <button hx-delete="/e/{{$.Event.Slug}}/rsvp/{{.RsvpID}}"
               hx-target="#slots-container"
               hx-swap="innerHTML settle:0.1s"
@@ -54,6 +54,27 @@
     <span class="nobody">no one yet</span>
   {{end}}
 </div>
+
+{{if .NotGoingList}}
+<div class="section-label">Can't make it ({{len .NotGoingList}})</div>
+<div class="rsvp-list">
+  {{range .NotGoingList}}
+  <span class="claim-chip" style="opacity:0.6">
+    {{if $.CanEditRsvps}}<span class="rsvp-name-link"
+      hx-get="/e/{{$.Event.Slug}}/rsvp/{{.RsvpID}}/edit"
+      hx-target="#edit-modal"
+      hx-swap="innerHTML">{{.Name}}</span>{{else}}{{.Name}}{{end}}{{if .Note}} <small style="color:#888">({{.Note}})</small>{{end}}
+    {{if $.CanEditRsvps}}
+    <button hx-delete="/e/{{$.Event.Slug}}/rsvp/{{.RsvpID}}"
+            hx-target="#slots-container"
+            hx-swap="innerHTML settle:0.1s"
+            hx-confirm="Remove {{.Name}}?"
+            title="Remove">&#215;</button>
+    {{end}}
+  </span>
+  {{end}}
+</div>
+{{end}}
 {{end}}
 
 {{define "slots.html"}}{{template "slots-inner" .}}{{end}}