feat!: upgrade to SvelteKit 3 and adapter-bun

- run sv migrate sveltekit-3: config moves into vite.config.ts, $lib becomes
  #lib, $env/dynamic becomes $app/env/private via src/env.ts, $app/environment
  becomes $app/env, hook types move to @sveltejs/kit/hooks
- env vars stay optional (the migrator defaulted them to ''), and BANCHO_MODE,
  which it missed, is declared and passed to simulatorEnabled
- handleError only logs and masks unknown errors; Kit 3 now routes 404s and
  error(...) through it too
- json()/text() become Response.json()/new Response(); goto keepFocus/noScroll
  becomes reset: false; invalidateAll becomes refreshAll; page.url is copied
  before mutating
- replace adapter-node with @sveltejs/adapter-bun; prod-server.ts wraps
  Bun.serve to add native WebSockets (bunSockets) for /ws paths, since the
  generated server has no websocket option
- drop the Kit readdir patch: Kit 3 sorts route entries itself
- match view and broadcast pages use the live score modules

BREAKING CHANGE: requires SvelteKit 3, TypeScript 6 and Bun 1.4; the build
output is build/index.js from adapter-bun, started through prod-server.ts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

eslint.config.js

@@ -6,7 +6,9 @@ import svelte from 'eslint-plugin-svelte';
 import { defineConfig } from 'eslint/config';
 import globals from 'globals';
 import ts from 'typescript-eslint';
-import svelteConfig from './svelte.config.js';
+import { loadConfig } from '@sveltejs/load-config';
+
+const svelteConfig = (await loadConfig('./', { traverse: false }))?.config;
 
 const gitignorePath = path.resolve(import.meta.dirname, '.gitignore');