Rename viz mode 'Side-by-side' label to 'Both'

app.py

@@ -1142,7 +1142,7 @@ else:
 VIZ_CHOICES = [
     ("Selection — kept patches in color, others fade to gray-white", "selection"),
     ("Heatmap — full-frame JET overlay (blue=low, red=high)",         "heatmap"),
-    ("Side-by-side — selection on the left, heatmap on the right",   "sbs"),
+    ("Both",                                                         "sbs"),
 ]
 SIGNAL_CHOICES = [
     ("Gradient — intra-frame Sobel (sharp edges, textures, text)",    "gradient"),