Add 'Reset demos' button to refresh canonical demo files

Existing accounts (including admin) seeded before new demos shipped
had no easy way to pull in the latest copies — the registration-time
seeder is intentionally non-destructive. The new badge action fetches
src/static/bundled-demos/manifest.json, confirms the overwrite, and
re-copies each canonical demo into code/. Open tabs of those files are
refreshed in place so the user sees the new content immediately.

src/static/bundled-demos/ ships the six canonical files plus the
manifest so this works in local mode and on a static-only host. The
Dockerfile now mirrors workspace/code/<demo>.py into bundled-demos/
during the image build, keeping the two locations in sync.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/static/bundled-demos/pin_demo.py

@@ -0,0 +1,54 @@
+"""Pin features demo.
+
+A "Pins" panel appears below the editor while this script runs:
+
+  * Pin 2 (OUT)  — blinks every 200 ms; the indicator follows along.
+  * Pin 4 (OUT)  — chases through .on() / .off() / .toggle().
+  * Pin 0 (IN)   — click the toggle button in the panel to flip its value.
+                   When it goes 0 -> 1 we register an IRQ that toggles pin 2.
+  * Pin 13 (PWM) — duty sweeps up and down; the bar shows the live duty cycle.
+"""
+
+import time
+
+from machine import Pin, PWM
+
+
+led_a = Pin(2, Pin.OUT)
+led_b = Pin(4, Pin.OUT)
+button = Pin(0, Pin.IN, Pin.PULL_UP)
+fader = PWM(Pin(13), freq=1000, duty_u16=0)
+
+
+def on_button(pin):
+    print("[irq] button rising edge -> toggling pin 2")
+    led_a.toggle()
+
+
+button.irq(handler=on_button, trigger=Pin.IRQ_RISING)
+
+
+tick = 0
+duty = 0
+direction = 1024
+
+while True:
+    led_a.value(tick % 2)
+    if tick % 4 == 0:
+        led_b.on()
+    elif tick % 4 == 2:
+        led_b.off()
+
+    duty += direction
+    if duty >= 65535:
+        duty = 65535
+        direction = -1024
+    elif duty <= 0:
+        duty = 0
+        direction = 1024
+    fader.duty_u16(duty)
+
+    button.value()
+
+    tick += 1
+    time.sleep(0.1)