feat(feedback): in-app user feedback with admin review and account roles

User-facing Feedback screen (Settings -> Info, registered accounts only): a
message (<=1024 runes) plus one optional attachment, an anti-spam gate (one
unreviewed message at a time), and the operator's inline reply with a
Settings/Info badge. Server-rendered admin console section (/_gm/feedback):
unread/read/archived queue with per-user search, detail with read/reply/
archive/delete/delete-all, safe attachment serving (nosniff, images inline via
<img>, others download-only). Introduces account_roles, the first per-account
role table; feedback_banned blocks only feedback submission, granted/revoked
from /users and the delete-with-block action.

- migration 00004_feedback (feedback_messages + account_roles) + jetgen
- backend internal/feedback (store+service), internal/account/roles.go
- wire: FlatBuffers feedback.submit/get/unread; gateway guest gate (Op.NonGuest,
  is_guest via session resolve) -> guest_forbidden before any backend call
- reply push reuses NotificationEvent with a new admin_reply sub-kind
- UI: /feedback route + screen, attachment picker, badge, channel detection, i18n
- tests: feedback unit (Go+UI), gateway guest-gate, inttest lifecycle, e2e
- docs: PLAN stage 19, ARCHITECTURE s15, FUNCTIONAL(+ru), TESTING, READMEs

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

@@ -0,0 +1,104 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+import * as flatbuffers from 'flatbuffers';
+
+export class FeedbackSubmitRequest {
+  bb: flatbuffers.ByteBuffer|null = null;
+  bb_pos = 0;
+  __init(i:number, bb:flatbuffers.ByteBuffer):FeedbackSubmitRequest {
+  this.bb_pos = i;
+  this.bb = bb;
+  return this;
+}
+
+static getRootAsFeedbackSubmitRequest(bb:flatbuffers.ByteBuffer, obj?:FeedbackSubmitRequest):FeedbackSubmitRequest {
+  return (obj || new FeedbackSubmitRequest()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+static getSizePrefixedRootAsFeedbackSubmitRequest(bb:flatbuffers.ByteBuffer, obj?:FeedbackSubmitRequest):FeedbackSubmitRequest {
+  bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+  return (obj || new FeedbackSubmitRequest()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+body():string|null
+body(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+body(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+attachment(index: number):number|null {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.readUint8(this.bb!.__vector(this.bb_pos + offset) + index) : 0;
+}
+
+attachmentLength():number {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
+}
+
+attachmentArray():Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? new Uint8Array(this.bb!.bytes().buffer, this.bb!.bytes().byteOffset + this.bb!.__vector(this.bb_pos + offset), this.bb!.__vector_len(this.bb_pos + offset)) : null;
+}
+
+attachmentName():string|null
+attachmentName(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+attachmentName(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+channel():string|null
+channel(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+channel(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 10);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+static startFeedbackSubmitRequest(builder:flatbuffers.Builder) {
+  builder.startObject(4);
+}
+
+static addBody(builder:flatbuffers.Builder, bodyOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(0, bodyOffset, 0);
+}
+
+static addAttachment(builder:flatbuffers.Builder, attachmentOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(1, attachmentOffset, 0);
+}
+
+static createAttachmentVector(builder:flatbuffers.Builder, data:number[]|Uint8Array):flatbuffers.Offset {
+  builder.startVector(1, data.length, 1);
+  for (let i = data.length - 1; i >= 0; i--) {
+    builder.addInt8(data[i]!);
+  }
+  return builder.endVector();
+}
+
+static startAttachmentVector(builder:flatbuffers.Builder, numElems:number) {
+  builder.startVector(1, numElems, 1);
+}
+
+static addAttachmentName(builder:flatbuffers.Builder, attachmentNameOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(2, attachmentNameOffset, 0);
+}
+
+static addChannel(builder:flatbuffers.Builder, channelOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(3, channelOffset, 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 {
+  FeedbackSubmitRequest.startFeedbackSubmitRequest(builder);
+  FeedbackSubmitRequest.addBody(builder, bodyOffset);
+  FeedbackSubmitRequest.addAttachment(builder, attachmentOffset);
+  FeedbackSubmitRequest.addAttachmentName(builder, attachmentNameOffset);
+  FeedbackSubmitRequest.addChannel(builder, channelOffset);
+  return FeedbackSubmitRequest.endFeedbackSubmitRequest(builder);
+}
+}