fix(esp32): add GPIO 16/17 pin aliases on DevKit V1 (RX2/TX2)

On the ESP32 DevKit V1 the silkscreen labels GPIO 16 / 17 as RX2 / TX2,
and Esp32Element.PINS_ESP32 only exposed the silkscreen names. Examples
that wire to numeric pin "16" or "17" (e.g. ledcAttach(16, 5000, 8) on
esp32-pwm-led-rgb) couldn't resolve those names — pinPositionCalculator
failed lookups, the wire endpoint fell back to (0,0)/(50,50) and the
LED component visually floated off the board, breaking the SPICE
netlist for the example.

Add "16" and "17" as aliases pointing to the same (134,143) / (134,131)
coordinates as RX2 / TX2 so both naming conventions resolve to the same
physical pin tip.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/velxio-components/Esp32Element.ts

@@ -50,7 +50,14 @@ const PINS_ESP32 = [
   { name: '2', x: 134, y: 169 },
   { name: '4', x: 134, y: 156 },
   { name: 'RX2', x: 134, y: 143 },
+  // RX2 is the silkscreen label for GPIO 16. Sketches that wire to pin
+  // '16' (e.g. ledcAttach(16, …) or any example referencing GPIO 16)
+  // must land on this same coordinate, otherwise pinPositionCalculator
+  // can't resolve the wire endpoint and the wire visually floats off
+  // the board. Same story for TX2 / 17 below.
+  { name: '16', x: 134, y: 143 },
   { name: 'TX2', x: 134, y: 131 },
+  { name: '17', x: 134, y: 131 },
   { name: '5', x: 134, y: 118 },
   { name: '18', x: 134, y: 105 },
   { name: '19', x: 134, y: 93 },