refactor(deploy): separate Dev/UAT into independent full-stack environments

- Each environment now runs its own PB + LiveKit + Voice Token + frontend
- UAT LiveKit: 7890, Voice Token: 7893 (separate from Dev 7880/7883)
- Remove docker-compose.backend.yml, merge into dev compose
- Delete duplicate bulletin migration files that caused PB crash on startup
- Update CLAUDE.md, nginx configs, and .env files accordingly

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/pb_migrations/1776749288_updated_game_blacklist.js

@@ -0,0 +1,16 @@
+/// <reference path="../pb_data/types.d.ts" />
+migrate((db) => {
+  const dao = new Dao(db)
+  const collection = dao.findCollectionByNameOrId("gblacklist_col")
+
+  collection.updateRule = "reporter = @request.auth.id"
+
+  return dao.saveCollection(collection)
+}, (db) => {
+  const dao = new Dao(db)
+  const collection = dao.findCollectionByNameOrId("gblacklist_col")
+
+  collection.updateRule = null
+
+  return dao.saveCollection(collection)
+})