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.

backend/internal/adminconsole/templates/pages/feedback_detail.gohtml

@@ -9,7 +9,7 @@
 <li><b>Interface language</b> {{.InterfaceLanguage}}</li>
 <li><b>App version</b> {{if .Version}}<code>{{.Version}}</code>{{else}}<span class="note">unknown</span>{{end}}</li>
 <li><b>IP</b> {{if .IP}}<code>{{.IP}}</code>{{else}}<span class="note">none</span>{{end}}</li>
-<li><b>Filed</b> {{.CreatedAt}} UTC{{if .CreatedAtLocal}} &middot; {{.CreatedAtLocal}} ({{.TimeZone}}){{end}}</li>
+<li><b>Filed</b> {{.CreatedAt}} UTC &middot; browser {{if .CreatedAtBrowser}}{{.CreatedAtBrowser}} ({{.BrowserTZ}}){{else}}<span class="note">N/A</span>{{end}} &middot; user {{if .CreatedAtUser}}{{.CreatedAtUser}} ({{.UserTZ}}){{else}}<span class="note">N/A</span>{{end}}</li>
 <li><b>State</b> {{if .Archived}}archived{{else if .Read}}read{{else}}<span class="warn">unread</span>{{end}}</li>
 {{if .Banned}}<li><b>Feedback</b> <span class="warn">sender is banned from feedback</span></li>{{end}}
 </ul>