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.

ui/src/lib/codec.ts

@@ -489,17 +489,20 @@ export function encodeFeedbackSubmit(
   attachment: Uint8Array | null,
   attachmentName: string,
   channel: string,
+  version: string,
 ): Uint8Array {
   const b = new Builder(256);
   const bodyOff = b.createString(body);
   const attOff = attachment && attachment.length > 0 ? fb.FeedbackSubmitRequest.createAttachmentVector(b, attachment) : 0;
   const nameOff = b.createString(attachmentName);
   const chOff = b.createString(channel);
+  const verOff = b.createString(version);
   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);
   return finish(b, fb.FeedbackSubmitRequest.endFeedbackSubmitRequest(b));
 }