fix: add ETag and headers to 304 Not Modified responses

AWS SDK requires ETag header in 304 responses. Without it, the SDK
throws UnknownError despite receiving a valid 304 status code.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/interfaces/http/controllers/s3-controller.ts

@@ -477,6 +477,7 @@ const handleGetObject = async (
 
   // H3: Conditional headers — If-Match / If-None-Match
   const etag = `"${file.fileHash || nanoid(16)}"`;
+  const lastModified = file.createdAt instanceof Date ? file.createdAt : new Date(file.createdAt);
   const ifMatch = headers['if-match'];
   if (ifMatch && ifMatch !== '*' && ifMatch !== etag) {
     return s3ErrorResponse(
@@ -489,22 +490,33 @@ const handleGetObject = async (
   }
   const ifNoneMatch = headers['if-none-match'];
   if (ifNoneMatch && ifNoneMatch === etag) {
-    return new Response(null, { status: 304, headers: s3Headers(reqId, {
-      etag, 'content-type': file.mimeType, 'content-length': String(file.sizeBytes),
-      'last-modified': lastModified.toUTCString(), 'x-amz-version-id': 'null',
-    }) });
+    return new Response(null, {
+      status: 304,
+      headers: s3Headers(reqId, {
+        etag,
+        'content-type': file.mimeType,
+        'content-length': String(file.sizeBytes),
+        'last-modified': lastModified.toUTCString(),
+        'x-amz-version-id': 'null',
+      }),
+    });
   }
 
   // H3: Conditional headers — If-Modified-Since / If-Unmodified-Since
-  const lastModified = file.createdAt instanceof Date ? file.createdAt : new Date(file.createdAt);
   const ifModifiedSince = headers['if-modified-since'];
   if (ifModifiedSince) {
     const since = new Date(ifModifiedSince);
     if (!Number.isNaN(since.getTime()) && lastModified.getTime() <= since.getTime()) {
-      return new Response(null, { status: 304, headers: s3Headers(reqId, {
-        etag, 'content-type': file.mimeType, 'content-length': String(file.sizeBytes),
-        'last-modified': lastModified.toUTCString(), 'x-amz-version-id': 'null',
-      }) });
+      return new Response(null, {
+        status: 304,
+        headers: s3Headers(reqId, {
+          etag,
+          'content-type': file.mimeType,
+          'content-length': String(file.sizeBytes),
+          'last-modified': lastModified.toUTCString(),
+          'x-amz-version-id': 'null',
+        }),
+      });
     }
   }
   const ifUnmodifiedSince = headers['if-unmodified-since'];
@@ -733,6 +745,7 @@ const handleHeadObject = async (
 
   // H3: Conditional headers for HEAD — If-Match / If-None-Match
   const etag = `"${file.fileHash || nanoid(16)}"`;
+  const lastModified = file.createdAt instanceof Date ? file.createdAt : new Date(file.createdAt);
   const ifMatch = headers['if-match'];
   if (ifMatch && ifMatch !== '*' && ifMatch !== etag) {
     return s3ErrorResponse(
@@ -745,22 +758,33 @@ const handleHeadObject = async (
   }
   const ifNoneMatch = headers['if-none-match'];
   if (ifNoneMatch && ifNoneMatch === etag) {
-    return new Response(null, { status: 304, headers: s3Headers(reqId, {
-      etag, 'content-type': file.mimeType, 'content-length': String(file.sizeBytes),
-      'last-modified': lastModified.toUTCString(), 'x-amz-version-id': 'null',
-    }) });
+    return new Response(null, {
+      status: 304,
+      headers: s3Headers(reqId, {
+        etag,
+        'content-type': file.mimeType,
+        'content-length': String(file.sizeBytes),
+        'last-modified': lastModified.toUTCString(),
+        'x-amz-version-id': 'null',
+      }),
+    });
   }
 
   // H3: Conditional headers for HEAD — If-Modified-Since / If-Unmodified-Since
-  const lastModified = file.createdAt instanceof Date ? file.createdAt : new Date(file.createdAt);
   const ifModifiedSince = headers['if-modified-since'];
   if (ifModifiedSince) {
     const since = new Date(ifModifiedSince);
     if (!Number.isNaN(since.getTime()) && lastModified.getTime() <= since.getTime()) {
-      return new Response(null, { status: 304, headers: s3Headers(reqId, {
-        etag, 'content-type': file.mimeType, 'content-length': String(file.sizeBytes),
-        'last-modified': lastModified.toUTCString(), 'x-amz-version-id': 'null',
-      }) });
+      return new Response(null, {
+        status: 304,
+        headers: s3Headers(reqId, {
+          etag,
+          'content-type': file.mimeType,
+          'content-length': String(file.sizeBytes),
+          'last-modified': lastModified.toUTCString(),
+          'x-amz-version-id': 'null',
+        }),
+      });
     }
   }
   const ifUnmodifiedSince = headers['if-unmodified-since'];

src/utils/s3/auth.ts

@@ -297,7 +297,7 @@ export const verifySignature = async (
   const hashedCanonicalRequest = await sha256Hex(canonicalRequest);
 
   // M1: Fall back to Date header if x-amz-date is missing
-  const amzDate = headers['x-amz-date'] || headers['date'] || '';
+  const amzDate = headers['x-amz-date'] || headers.date || '';
 
   // H5: Validate request freshness (clock skew / replay protection)
   if (amzDate) {