fix: resolve file library Open File bug, upload reliability, and SSE proxy timeouts (#203)

The Open File button in the Files section did nothing due to a race
condition where the home page reset the file store on mount before files
from handleOpenFile could render. Upload on the files page used fetch
with no timeout, progress, or retry, causing silent failures on mobile
and slow connections. SSE connections for job progress had no keepalive
pings, allowing reverse proxies to kill idle streams.

apps/web/src/lib/api.ts

@@ -237,26 +237,56 @@ export async function apiGetFileDetails(id: string): Promise<UserFileDetail> {
   return { ...res.file, versions: res.versions };
 }
 
-export async function apiUploadUserFiles(
+export function apiUploadUserFiles(
   files: File[],
+  onProgress?: (percent: number) => void,
 ): Promise<{ files: Array<{ id: string; originalName: string; size: number; version: number }> }> {
-  const formData = new FormData();
-  for (const f of files) formData.append("files", f);
-  let res: Response;
-  try {
-    res = await fetch("/api/v1/files/upload", {
-      method: "POST",
-      headers: formatHeaders(),
-      body: formData,
+  return new Promise((resolve, reject) => {
+    const formData = new FormData();
+    for (const f of files) formData.append("files", f);
+
+    const xhr = new XMLHttpRequest();
+    xhr.open("POST", "/api/v1/files/upload");
+    xhr.timeout = 120_000;
+
+    const headers = formatHeaders();
+    headers.forEach((value, key) => {
+      if (key.toLowerCase() !== "content-type") {
+        xhr.setRequestHeader(key, value);
+      }
     });
-  } catch (error) {
-    if (error instanceof TypeError) {
-      useConnectionStore.getState().setDisconnected();
+
+    if (onProgress) {
+      xhr.upload.onprogress = (e) => {
+        if (e.lengthComputable) {
+          onProgress(Math.round((e.loaded / e.total) * 100));
+        }
+      };
     }
-    throw error;
-  }
-  if (!res.ok) throw new Error(`Upload failed: ${res.status}`);
-  return res.json();
+
+    xhr.onload = () => {
+      if (xhr.status >= 200 && xhr.status < 300) {
+        try {
+          resolve(JSON.parse(xhr.responseText));
+        } catch {
+          reject(new Error("Invalid server response"));
+        }
+      } else {
+        reject(new Error(`Upload failed: ${xhr.status}`));
+      }
+    };
+
+    xhr.onerror = () => {
+      useConnectionStore.getState().setDisconnected();
+      reject(new TypeError("Network error"));
+    };
+
+    xhr.ontimeout = () => {
+      reject(new Error("Upload timed out"));
+    };
+
+    xhr.send(formData);
+  });
 }
 
 export async function apiDeleteUserFiles(ids: string[]): Promise<{ deleted: number }> {