feat(feedback): capture the app version; show version + local Filed time

Each feedback submission now carries the client app version (__APP_VERSION__),
snapshotted like the interface language: FlatBuffers FeedbackSubmitRequest gains
a version field → gateway transcode → backend, persisted in a new nullable
feedback_messages.app_version column (migration 00003, additive so an image
rollback stays DB-safe). The operator console detail shows the app version and
renders the Filed time in UTC plus the sender's time zone (fmtTimeIn).

Touches: fbs schema + regenerated Go/TS codegen, codec + transport (the client
attaches its build), gateway transcode + backendclient, feedback store/service,
admin view + template, docs (ARCHITECTURE §15, FUNCTIONAL + _ru). Verified:
feedback integration tests (migration + version round-trip), codec round-trip,
check/unit/build green.

backend/internal/server/handlers_admin_feedback.go

@@ -77,6 +77,11 @@ func (s *Server) consoleFeedbackDetail(c *gin.Context) {
 		s.consoleError(c, err)
 		return
 	}
+	// Filed time: always UTC; plus the sender's local zone when it is set and not UTC.
+	localCreated := ""
+	if m.TimeZone != "" && m.TimeZone != "UTC" {
+		localCreated = fmtTimeIn(m.CreatedAt, m.TimeZone)
+	}
 	view := adminconsole.FeedbackDetailView{
 		ID: m.ID.String(), AccountID: m.AccountID.String(), SenderName: m.SenderName,
 		Source: m.Source, Channel: m.Channel, InterfaceLanguage: m.Lang,
@@ -84,6 +89,7 @@ func (s *Server) consoleFeedbackDetail(c *gin.Context) {
 		HasAttachment: m.HasAttachment, AttachmentName: m.AttachmentName, IsImage: feedback.IsImage(m.AttachmentName),
 		Read: m.Read, Archived: m.Archived, Replied: m.Replied, ReplyBody: m.ReplyBody,
 		RepliedAt: fmtTime(m.RepliedAt), CreatedAt: fmtTime(m.CreatedAt),
+		Version: m.Version, CreatedAtLocal: localCreated, TimeZone: m.TimeZone,
 	}
 	if banned, err := s.accounts.HasRole(ctx, m.AccountID, account.RoleFeedbackBanned); err == nil {
 		view.Banned = banned