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/adminconsole/templates/pages/feedback_detail.gohtml

@@ -7,8 +7,9 @@
 <li><b>From</b> <a href="/_gm/users/{{.AccountID}}">{{.SenderName}}</a> ({{.Source}})</li>
 <li><b>Channel</b> {{.Channel}}</li>
 <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}}</li>
+<li><b>Filed</b> {{.CreatedAt}} UTC{{if .CreatedAtLocal}} &middot; {{.CreatedAtLocal}} ({{.TimeZone}}){{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>

backend/internal/adminconsole/views.go

@@ -554,5 +554,11 @@ type FeedbackDetailView struct {
 	ReplyBody         string
 	RepliedAt         string
 	CreatedAt         string
-	Banned            bool
+	// Version is the client app build the report was sent from (empty for rows that predate it).
+	Version string
+	// CreatedAtLocal is CreatedAt rendered in the sender's time zone, with TimeZone its label.
+	// Empty when the sender's zone is UTC or unknown — then only the UTC CreatedAt is shown.
+	CreatedAtLocal string
+	TimeZone       string
+	Banned         bool
 }