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.

pkg/fbs/scrabblefb/FeedbackSubmitRequest.go

@@ -107,8 +107,16 @@ func (rcv *FeedbackSubmitRequest) Version() []byte {
 	return nil
 }
 
+func (rcv *FeedbackSubmitRequest) BrowserTz() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(14))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
 func FeedbackSubmitRequestStart(builder *flatbuffers.Builder) {
-	builder.StartObject(5)
+	builder.StartObject(6)
 }
 func FeedbackSubmitRequestAddBody(builder *flatbuffers.Builder, body flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(body), 0)
@@ -128,6 +136,9 @@ func FeedbackSubmitRequestAddChannel(builder *flatbuffers.Builder, channel flatb
 func FeedbackSubmitRequestAddVersion(builder *flatbuffers.Builder, version flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(4, flatbuffers.UOffsetT(version), 0)
 }
+func FeedbackSubmitRequestAddBrowserTz(builder *flatbuffers.Builder, browserTz flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(5, flatbuffers.UOffsetT(browserTz), 0)
+}
 func FeedbackSubmitRequestEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
 	return builder.EndObject()
 }