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/docs_prose.py

@@ -18,7 +18,9 @@ DOCS_PAGES = [
     {"slug": "join", "title": "Joining", "section": "Start here", "file": "join.md"},
     {"slug": "legal", "title": "Terms and privacy", "section": "Start here", "file": "legal.md"},
     {"slug": "api", "title": "API and authentication", "section": "Building with the API", "file": "api.md"},
+    {"slug": "content", "title": "Galleries and content", "section": "Start here", "file": "content.md"},
     {"slug": "admin", "title": "Admin and services", "section": "Admin", "file": "admin.md", "admin": True},
+    {"slug": "operator", "title": "Operator runbook", "section": "Admin", "file": "operator.md", "admin": True},
     {"slug": "backups", "title": "Backups and maintenance", "section": "Admin", "file": "backups.md", "admin": True},
 ]