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/server/handlers.go

@@ -12,6 +12,7 @@ import (
 	"scrabble/backend/internal/account"
 	"scrabble/backend/internal/accountmerge"
 	"scrabble/backend/internal/engine"
+	"scrabble/backend/internal/feedback"
 	"scrabble/backend/internal/game"
 	"scrabble/backend/internal/lobby"
 	"scrabble/backend/internal/session"
@@ -77,6 +78,11 @@ func (s *Server) registerRoutes() {
 		u.PUT("/games/:id/draft", s.handleSaveDraft)
 		u.POST("/games/:id/hide", s.handleHideGame)
 	}
+	if s.feedback != nil {
+		u.POST("/feedback", s.handleFeedbackSubmit)
+		u.GET("/feedback", s.handleFeedbackState)
+		u.GET("/feedback/unread", s.handleFeedbackUnread)
+	}
 	if s.matchmaker != nil {
 		u.POST("/lobby/enqueue", s.handleEnqueue)
 	}
@@ -232,6 +238,20 @@ func statusForError(err error) (int, string) {
 		return http.StatusConflict, "request_declined"
 	case errors.Is(err, social.ErrFriendCodeInvalid):
 		return http.StatusUnprocessableEntity, "friend_code_invalid"
+	case errors.Is(err, feedback.ErrGuestForbidden):
+		return http.StatusForbidden, "feedback_guest_forbidden"
+	case errors.Is(err, feedback.ErrBanned):
+		return http.StatusForbidden, "feedback_banned"
+	case errors.Is(err, feedback.ErrPendingReview):
+		return http.StatusConflict, "feedback_pending"
+	case errors.Is(err, feedback.ErrEmptyMessage):
+		return http.StatusUnprocessableEntity, "feedback_empty"
+	case errors.Is(err, feedback.ErrMessageTooLong):
+		return http.StatusUnprocessableEntity, "feedback_too_long"
+	case errors.Is(err, feedback.ErrAttachmentTooLarge):
+		return http.StatusUnprocessableEntity, "feedback_attachment_too_large"
+	case errors.Is(err, feedback.ErrAttachmentType):
+		return http.StatusUnprocessableEntity, "feedback_attachment_type"
 	default:
 		return http.StatusInternalServerError, "internal"
 	}