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.

ui/src/lib/codec.ts

@@ -490,6 +490,7 @@ export function encodeFeedbackSubmit(
   attachmentName: string,
   channel: string,
   version: string,
+  browserTz: string,
 ): Uint8Array {
   const b = new Builder(256);
   const bodyOff = b.createString(body);
@@ -497,12 +498,14 @@ export function encodeFeedbackSubmit(
   const nameOff = b.createString(attachmentName);
   const chOff = b.createString(channel);
   const verOff = b.createString(version);
+  const tzOff = b.createString(browserTz);
   fb.FeedbackSubmitRequest.startFeedbackSubmitRequest(b);
   fb.FeedbackSubmitRequest.addBody(b, bodyOff);
   if (attOff) fb.FeedbackSubmitRequest.addAttachment(b, attOff);
   fb.FeedbackSubmitRequest.addAttachmentName(b, nameOff);
   fb.FeedbackSubmitRequest.addChannel(b, chOff);
   fb.FeedbackSubmitRequest.addVersion(b, verOff);
+  fb.FeedbackSubmitRequest.addBrowserTz(b, tzOff);
   return finish(b, fb.FeedbackSubmitRequest.endFeedbackSubmitRequest(b));
 }