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/utils/s3/auth.ts

@@ -131,8 +131,8 @@ export const verifySignature = async (
   s3SecretKey: string,
   region: string,
 ): Promise<SigV4Result> => {
-  const authHeader = headers['authorization'];
-  if (!authHeader || !authHeader.startsWith('AWS4-HMAC-SHA256')) {
+  const authHeader = headers.authorization;
+  if (!authHeader?.startsWith('AWS4-HMAC-SHA256')) {
     return { isValid: false, credential: null, errorCode: 'AccessDenied' };
   }
 
@@ -276,6 +276,6 @@ export const verifyPresignedUrl = async (
 };
 
 export const isS3Request = (headers: Record<string, string>): boolean => {
-  const auth = headers['authorization'] || '';
+  const auth = headers.authorization || '';
   return auth.startsWith('AWS4-HMAC-SHA256');
 };