feat(feedback): in-app user feedback with admin review and account roles

User-facing Feedback screen (Settings -> Info, registered accounts only): a
message (<=1024 runes) plus one optional attachment, an anti-spam gate (one
unreviewed message at a time), and the operator's inline reply with a
Settings/Info badge. Server-rendered admin console section (/_gm/feedback):
unread/read/archived queue with per-user search, detail with read/reply/
archive/delete/delete-all, safe attachment serving (nosniff, images inline via
<img>, others download-only). Introduces account_roles, the first per-account
role table; feedback_banned blocks only feedback submission, granted/revoked
from /users and the delete-with-block action.

- migration 00004_feedback (feedback_messages + account_roles) + jetgen
- backend internal/feedback (store+service), internal/account/roles.go
- wire: FlatBuffers feedback.submit/get/unread; gateway guest gate (Op.NonGuest,
  is_guest via session resolve) -> guest_forbidden before any backend call
- reply push reuses NotificationEvent with a new admin_reply sub-kind
- UI: /feedback route + screen, attachment picker, badge, channel detection, i18n
- tests: feedback unit (Go+UI), gateway guest-gate, inttest lifecycle, e2e
- docs: PLAN stage 19, ARCHITECTURE s15, FUNCTIONAL(+ru), TESTING, READMEs

backend/internal/adminconsole/assets/console.css

@@ -116,3 +116,8 @@ code { background: var(--bg); padding: 0.05rem 0.3rem; border-radius: 4px; }
 .lg-min { color: var(--ok); }
 .lg-avg { color: var(--accent); }
 .lg-max { color: var(--danger); }
+
+/* Feedback: user-controlled message bodies are wrapped and escaped (never HTML);
+   an image attachment is previewed inline, bounded so it cannot dominate the page. */
+.msgbody { white-space: pre-wrap; word-break: break-word; background: var(--bg); padding: 0.6rem 0.8rem; border-radius: 6px; margin: 0.6rem 0; }
+.attach { max-width: 100%; max-height: 480px; height: auto; border: 1px solid var(--line); border-radius: 6px; }