Member invites, gallery resync, content and operator docs

- Invite flow: admin issue/revoke on join requests, public single-use
  claim links (hash-only tokens, 7-day expiry, no state reveal), claim
  creates the Member account and marks the request accepted
- Gallery: admin status page plus resync endpoint; sync refreshes
  thumbnails whose content changed; tools/gallery contract and checker
- Docs: public content page, admin-only operator runbook, api.md
  invite/gallery sections, all routes in the live API docs, docs
  reachability gate test
- Screenshots cover the new pages; version 1.0.18

molodetz/templates/admin/joins.html

@@ -12,7 +12,7 @@
     <td>{{ item.contact }}</td>
     <td>{% if item.repo_url %}<a href="{{ item.repo_url }}" rel="nofollow noopener" target="_blank">{{ item.repo_url }}</a>{% if item.link_status %}<br><span class="muted">{{ item.link_status }}{% if item.link_title %}: {{ item.link_title }}{% endif %}</span>{% endif %}{% else %}<span class="muted">none</span>{% endif %}</td>
     <td>{{ item.message }}</td>
-    <td><span class="status {{ item.status }}">{{ item.status }}</span></td>
+    <td><span class="status {{ item.status }}">{{ item.status }}</span>{% if item.invite_open %}<br><span class="muted">invite until {{ local_dt(item.invite_expires_at) }}</span>{% endif %}</td>
     <td>{{ local_dt(item.created_at) }}</td>
     <td class="actions">
       <form method="post" action="/admin/joins/{{ item.uid }}/status">
@@ -20,6 +20,8 @@
         <button class="button ghost small" type="submit">Set</button>
       </form>
       {% if item.repo_url %}<form method="post" action="/admin/joins/{{ item.uid }}/check"><button class="button ghost small" type="submit" data-loading>Check link</button></form>{% endif %}
+      {% if item.invite_open %}<form method="post" action="/admin/joins/{{ item.uid }}/invite/revoke"><button class="button ghost small" type="submit">Revoke invite</button></form>
+      {% elif item.status != 'declined' %}<form method="post" action="/admin/joins/{{ item.uid }}/invite"><button class="button ghost small" type="submit" data-loading>Issue invite</button></form>{% endif %}
     </td>
   </tr>
   {% else %}