fix: corrupted binary downloads (#634)

- The existing setup was using the text reader endpoint for downloading
files `fsPromises.readFile(..., 'utf8')` at line 801. This was incorrect

- In the old Files tab flow, the client then took that decoded string
and rebuilt it as a text blob. That UTF-8 decode/re-encode step changes
raw bytes, so the downloaded file no longer matches the original.
Folder ZIP export had the same problem for any binary file inside the
archive.

Co-authored-by: Haileyesus <something@gmail.com>

src/utils/api.js

@@ -111,6 +111,8 @@ export const api = {
     }),
   readFile: (projectName, filePath) =>
     authenticatedFetch(`/api/projects/${projectName}/file?filePath=${encodeURIComponent(filePath)}`),
+  readFileBlob: (projectName, filePath) =>
+    authenticatedFetch(`/api/projects/${projectName}/files/content?path=${encodeURIComponent(filePath)}`),
   saveFile: (projectName, filePath, content) =>
     authenticatedFetch(`/api/projects/${projectName}/file`, {
       method: 'PUT',
@@ -242,4 +244,4 @@ export const api = {
     method: 'DELETE',
     ...options,
   }),
-};
+};