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>

tsconfig.json

@@ -1,20 +1,9 @@
 {
-	"extends": "./.svelte-kit/tsconfig.json",
+	"extends": "$app/tsconfig",
 	"compilerOptions": {
 		"rewriteRelativeImportExtensions": true,
-		"allowJs": true,
-		"checkJs": true,
-		"esModuleInterop": true,
-		"forceConsistentCasingInFileNames": true,
-		"resolveJsonModule": true,
-		"skipLibCheck": true,
 		"sourceMap": true,
-		"strict": true,
-		"moduleResolution": "bundler"
-	}
-	// Path aliases are handled by https://svelte.dev/docs/kit/configuration#alias
-	// except $lib which is handled by https://svelte.dev/docs/kit/configuration#files
-	//
-	// To make changes to top-level options such as include and exclude, we recommend extending
-	// the generated config; see https://svelte.dev/docs/kit/configuration#typescript
+		"strict": true
+	},
+	"include": ["src", "vite.config.ts", "drizzle.config.ts", "playwright.config.ts"]
 }