fix(forum): correct sidebar nesting and duplicate widget card

- keep .sidebar a sibling of .content-wrap inside main.container so the
  theme's float math puts it in the right column
- move fluid widget zones inside main on plate / post routes
- drop the leftover .forum-home .jio-widget-box override that stacked a
  second card background on the user card
- balance the compose page shell for guests and editors

tools/admin-contract-report.json

@@ -1,5 +1,5 @@
 {
-    "generated_at": "2026-11-11T10:06:02+00:00",
+    "generated_at": "2026-11-11T10:25:09+00:00",
     "errors": [],
     "warnings": [
         "customPage tools-update section 'tools/update' not in PHP schema (ok if pure operational page)",