Hide transient upload errors from queue UI

Transient network errors on first upload attempt showed ugly
'Network error: TypeError: Load failed' messages in the queue.
These are normal on iOS Safari and auto-resolve on retry.

- Clean up sync error messages (friendly text, no raw error types)
- Only show error messages in queue after 3+ retries or failed status
- Only show retry counter after 3+ retries
- First couple of retries are silent - just shows Pending status

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/static/js/sync.js

@@ -192,12 +192,10 @@ const Sync = {
             } catch (fetchErr) {
                 clearTimeout(timeoutId);
                 if (fetchErr.name === 'AbortError') {
-                    throw new Error('Upload timed out (' + (this.UPLOAD_TIMEOUT_MS / 1000) + 's)');
+                    throw new Error('Upload timed out');
                 }
-                // Capture detailed error info for debugging
-                const errDetail = fetchErr.name + ': ' + fetchErr.message;
-                console.error('[SYNC] Fetch threw:', errDetail);
-                throw new Error('Network error: ' + errDetail);
+                console.error('[SYNC] Fetch threw:', fetchErr.name, fetchErr.message);
+                throw new Error('Connection lost - will retry');
             }
             clearTimeout(timeoutId);
 
@@ -253,13 +251,12 @@ const Sync = {
 
         } catch (error) {
             this._setUploading(false);
-            const errMsg = (error.name || 'Error') + ': ' + error.message;
-            console.error('[SYNC] Upload failed:', errMsg, '(attempt', retryCount + 1 + ')');
+            console.error('[SYNC] Upload failed:', error.message, '(attempt', retryCount + 1 + ')');
             await Storage.updatePhoto(photo.id, {
                 status: 'pending',
                 retryCount: retryCount + 1,
-                lastError: errMsg,
-                error: errMsg
+                lastError: error.message,
+                error: error.message
             });
             return false;
         }