chore(lint): biome cleanup across services — format, sort imports, drop unused

- discord-gateway: 74 lint errors -> 0 (format, import sorting, unused
  imports/vars, dead breath var)
- backend: format + sort imports (11 warnings left: noExplicitAny)
- frontend: remove unused imports, drop dead breathing var, fix
  useExhaustiveDependencies (scroll keyed on messages), a11y biome-ignore
  for drag surface + stopPropagation container (mouse-only gestures)
- remaining warnings are false positives: index keys on static lists,
  <img> in static export (next/image unsupported), noExplicitAny

tsc --noEmit clean on all 3 services; vitest green (60+36).

services/backend/src/modules/voice/voice.controller.ts

@@ -1,5 +1,5 @@
-import { createChildLogger } from "@/shared/logger/index";
 import type { Request, Response } from "express";
+import { createChildLogger } from "@/shared/logger/index";
 import { asyncHandler } from "../../shared/middlewares/index.js";
 import { publishCommandNoReply } from "../../shared/redis/index.js";
 import type { ConnectVoiceInput, VoiceCommandInput } from "./voice.schema.js";

services/backend/src/modules/voice/voice.routes.ts

@@ -1,6 +1,6 @@
-import { createChildLogger } from "@/shared/logger/index";
 import type { Request, Response, Router } from "express";
 import express from "express";
+import { createChildLogger } from "@/shared/logger/index";
 import { asyncHandler, validateBody } from "../../shared/middlewares/index.js";
 import {
   handleConnectVoice,

services/backend/src/modules/voice/voice.service.ts

@@ -1,3 +1,9 @@
+import { eq } from "drizzle-orm";
+import {
+  createChildLogger,
+  tryCommandThenFallback,
+} from "../../shared/commandHelper.js";
+import { getDatabase } from "../../shared/database/index.js";
 import {
   COMMAND_GUILDS_LIST,
   COMMAND_GUILDS_TEXT_CHANNELS,
@@ -8,12 +14,6 @@ import {
   pgMessagesTable,
   VOICE_STATUS_KEY,
 } from "../../shared/index.js";
-import { eq } from "drizzle-orm";
-import {
-  createChildLogger,
-  tryCommandThenFallback,
-} from "../../shared/commandHelper.js";
-import { getDatabase } from "../../shared/database/index.js";
 import { publishCommand, readRedisStatus } from "../../shared/redis/index.js";
 
 const logger = createChildLogger("voice.service");