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

tests/api/docs/pages.py

@@ -0,0 +1,23 @@
+# retoor <retoor@molodetz.nl>
+import pytest
+
+from molodetz.docs_prose import DOCS_PAGES, PROSE_DIR, page_source, render_page
+
+
+def test_every_docs_page_has_source_and_renders():
+    for page in DOCS_PAGES:
+        assert (PROSE_DIR / page["file"]).is_file(), page["slug"]
+        assert page_source(page["slug"]).strip(), page["slug"]
+        assert render_page(page["slug"]).strip(), page["slug"]
+
+
+@pytest.mark.parametrize("page", DOCS_PAGES, ids=lambda page: page["slug"])
+def test_docs_page_reachability_matches_gate(page, anon, admin):
+    response = admin.get(f"/docs/{page['slug']}")
+    assert response.status_code == 200, page["slug"]
+    assert page["title"] in response.text
+    anon_response = anon.get(f"/docs/{page['slug']}")
+    if page.get("admin"):
+        assert anon_response.status_code == 404, page["slug"]
+    else:
+        assert anon_response.status_code == 200, page["slug"]