feat(feedback): capture the browser UTC offset; Filed time in three zones

The account time zone defaults to UTC until a player saves a profile, so a
report's Filed time could only render in UTC even for a player clearly in
another zone. Capture the client's detected "±HH:MM" offset (browser_tz) with
each submission and show the Filed time in three zones in the operator console
— UTC, the browser offset detected at submit, and the sender's saved profile
zone — each shown "N/A" when not known, so the operator can tell what is
certainly known from what is merely defaulted.

- Thread browser_tz through the fbs envelope (+ Go/TS codegen), the gateway
  transcode + backend client, and the backend feedback service/store; add the
  column via migration 00004 (additive, image-rollback-safe).
- Fix fmtTimeIn to resolve "±HH:MM" offsets via account.ResolveZone;
  time.LoadLocation alone silently fell back to UTC for offset zones, which is
  the second reason a "+02:00" sender showed only UTC.
- Update ARCHITECTURE/FUNCTIONAL(+ru) docs and the feedback integration test.

gateway/internal/transcode/transcode.go

@@ -499,7 +499,7 @@ func hideGameHandler(backend *backendclient.Client) Handler {
 func feedbackSubmitHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsFeedbackSubmitRequest(req.Payload, 0)
-		if err := backend.FeedbackSubmit(ctx, req.UserID, string(in.Body()), in.AttachmentBytes(), string(in.AttachmentName()), string(in.Channel()), string(in.Version()), req.ClientIP); err != nil {
+		if err := backend.FeedbackSubmit(ctx, req.UserID, string(in.Body()), in.AttachmentBytes(), string(in.AttachmentName()), string(in.Channel()), string(in.Version()), string(in.BrowserTz()), req.ClientIP); err != nil {
 			return nil, err
 		}
 		return encodeAck(true), nil