Fix spectrum visualisation for edge cases

App/app/spectrum.c

@@ -950,16 +950,16 @@ uint8_t Rssi2Y(uint16_t rssi)
                 // Total width units = (bars - 1) full bars + 2 half bars = bars
                 // First bar: half width, middle bars: full width, last bar: half width
                 // Scale: 128 pixels / (bars - 1) = pixels per full bar
-                uint16_t fullWidth = 128 * 2 / (bars - 1);  // x2 for precision
+                uint16_t fullWidth = (128 << 8) / (bars - 1);  // x256 for precision
                 
                 if (i == 0)
                 {
-                    x = fullWidth / 4;  // half of half (because fullWidth is x2)
+                    x = fullWidth / (2 << 8);  // half of /256 (because fullWidth is x256)
                 }
                 else
                 {
                     // Position = half + (i-1) full bars + current bar
-                    x = fullWidth / 4 + (uint16_t)i * fullWidth / 2;
+                    x = fullWidth / (2 << 8) + (uint16_t)i * fullWidth / (1 << 8);
                     if (i == bars - 1) x = 128;  // Last bar ends at screen edge
                 }
             }