fix: satisfy deploy lint gate for S3 compatibility work

- Apply Biome organize-import/formatting fixes across changed S3 files
- Replace remaining string concatenations with template literals for lint
- Make home page inline handlers explicit via window.* and add button types
- Clean S3 auth lint issues with dot-property access and optional chaining
- Keep GetObject proxy and production/S3 SDK tests passing

Verification:
- bun run lint (0 errors, 1 CSS specificity warning)
- S3_SECRET_KEY=<env> bun test test/production-e2e.test.ts (29 pass)
- S3_SECRET_KEY=<env> bun test test/s3-sdk.test.ts (20 pass)
- bun test test/s3-auth.test.ts (5 pass)

src/routes/home.ts

@@ -1,5 +1,5 @@
 export const handleHome = async (): Promise<Response> => {
-  const html = await Bun.file(import.meta.dir + '/../home.html').text();
+  const html = await Bun.file(`${import.meta.dir}/../home.html`).text();
   return new Response(html, {
     status: 200,
     headers: {