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/gen/fbs/scrabblefb/feedback-submit-request.ts

@@ -56,8 +56,15 @@ channel(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
+version():string|null
+version(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+version(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 12);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
 static startFeedbackSubmitRequest(builder:flatbuffers.Builder) {
-  builder.startObject(4);
+  builder.startObject(5);
 }
 
 static addBody(builder:flatbuffers.Builder, bodyOffset:flatbuffers.Offset) {
@@ -88,17 +95,22 @@ static addChannel(builder:flatbuffers.Builder, channelOffset:flatbuffers.Offset)
   builder.addFieldOffset(3, channelOffset, 0);
 }
 
+static addVersion(builder:flatbuffers.Builder, versionOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(4, versionOffset, 0);
+}
+
 static endFeedbackSubmitRequest(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createFeedbackSubmitRequest(builder:flatbuffers.Builder, bodyOffset:flatbuffers.Offset, attachmentOffset:flatbuffers.Offset, attachmentNameOffset:flatbuffers.Offset, channelOffset:flatbuffers.Offset):flatbuffers.Offset {
+static createFeedbackSubmitRequest(builder:flatbuffers.Builder, bodyOffset:flatbuffers.Offset, attachmentOffset:flatbuffers.Offset, attachmentNameOffset:flatbuffers.Offset, channelOffset:flatbuffers.Offset, versionOffset:flatbuffers.Offset):flatbuffers.Offset {
   FeedbackSubmitRequest.startFeedbackSubmitRequest(builder);
   FeedbackSubmitRequest.addBody(builder, bodyOffset);
   FeedbackSubmitRequest.addAttachment(builder, attachmentOffset);
   FeedbackSubmitRequest.addAttachmentName(builder, attachmentNameOffset);
   FeedbackSubmitRequest.addChannel(builder, channelOffset);
+  FeedbackSubmitRequest.addVersion(builder, versionOffset);
   return FeedbackSubmitRequest.endFeedbackSubmitRequest(builder);
 }
 }