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/README.md

@@ -130,6 +130,7 @@ internal/server/     # gin engine, route groups, X-User-ID middleware, probes
 internal/engine/     # in-process scrabble-solver bridge: registry, bag, Game, replay
 internal/game/       # game domain: lifecycle, journal+cache, hint, word-check, GCG, sweeper
 internal/social/     # friend graph, per-user blocks, per-game chat + nudge, content filter
+internal/feedback/   # user feedback: messages + attachment (bytea), anti-spam gate, admin review/reply
 internal/lobby/      # auto-match (DB-backed open games + robot substitution) + friend-game invitations
 internal/robot/      # human-like robot opponent: account pool, seed-derived strategy, move driver
 internal/adminconsole/ # server-rendered admin console (Go templates + embedded CSS, view models), served at /_gm