fix(log): fall back to user's Desktop before AppData, keep daily-log naming

If the configured log path (or the default exe-adjacent path) isn't
writable, we now try the current user's Desktop first — that's where
users actually look — and only fall back to AppData if Desktop is
also unavailable. The daily-log filename suffix is preserved on the
fallback file so the format stays consistent.

main.js

@@ -113,6 +113,25 @@ function getLogFilePath() {
   return _dailyLogPath;
 }
 
+function buildFallbackLogName(dir) {
+  // Match the daily-log naming when enabled, so fallback files stay consistent.
+  const config = configStore.load();
+  const useDailyLog = config && config.globalSettings && config.globalSettings.sessionLog;
+  if (!useDailyLog) return path.join(dir, 'fileuploader.log');
+  const now = new Date();
+  const pad = (n) => String(n).padStart(2, '0');
+  const today = `${now.getFullYear()}-${pad(now.getMonth() + 1)}-${pad(now.getDate())}`;
+  return path.join(dir, `fileuploader-${today}.log`);
+}
+
+function getSafeDesktopDir() {
+  try {
+    const desktop = app.getPath('desktop');
+    if (desktop && fs.existsSync(desktop)) return desktop;
+  } catch {}
+  return null;
+}
+
 let _uploadLogFallbackWarned = false;
 function appendUploadLog(hoster, link, fileName) {
   const now = new Date();
@@ -129,11 +148,30 @@ function appendUploadLog(hoster, link, fileName) {
     tryWrite(getLogFilePath());
     return;
   } catch (err) {
-    debugLog(`appendUploadLog primary failed (${err.message}); using fallback`);
+    debugLog(`appendUploadLog primary failed (${err.message}); trying desktop fallback`);
   }
 
+  // Fallback 1: current user's Desktop (visible, easy to find).
+  const desktop = getSafeDesktopDir();
+  if (desktop) {
     try {
-    const fallbackPath = path.join(app.getPath('userData'), 'fileuploader-fallback.log');
+      const fallbackPath = buildFallbackLogName(desktop);
+      tryWrite(fallbackPath);
+      if (!_uploadLogFallbackWarned) {
+        _uploadLogFallbackWarned = true;
+        if (mainWindow && !mainWindow.isDestroyed()) {
+          mainWindow.webContents.send('upload-log-fallback', { fallbackPath });
+        }
+      }
+      return;
+    } catch (err) {
+      debugLog(`appendUploadLog desktop fallback failed (${err.message}); trying userData`);
+    }
+  }
+
+  // Fallback 2: userData (always writable by the current user).
+  try {
+    const fallbackPath = buildFallbackLogName(app.getPath('userData'));
     tryWrite(fallbackPath);
     if (!_uploadLogFallbackWarned) {
       _uploadLogFallbackWarned = true;
@@ -142,7 +180,7 @@ function appendUploadLog(hoster, link, fileName) {
       }
     }
   } catch (err) {
-    debugLog(`appendUploadLog fallback also failed: ${err.message}`);
+    debugLog(`appendUploadLog all fallbacks failed: ${err.message}`);
   }
 }