feat: printer beep support for kitchen tickets

Adds configurable buzzer control so the printer alerts kitchen staff
on each new ticket print.

Backend:
  - printer_service.py: ESC 0x07 beep command fired before paper cut,
    reads print.beep_on_ticket / print.beep_pattern settings; supports
    single/double/triple/long presets and a custom:n1:n2:n3 format
  - settings.py: registers the two new print.beep_* settings with
    defaults (beep_on_ticket=true, beep_pattern=double)
  - system.py: POST /api/system/printers/test-beep endpoint for
    live testing from the dashboard

Frontend (PrintFontsTab):
  - BeepSection component with preset grid, custom n1/n2/n3 inputs,
    and a live test-beep button targeting any configured printer

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

local_backend/services/printer_service.py

@@ -66,6 +66,8 @@ _PRINT_SETTING_KEYS = [
     "print.font_ingredient",
     "print.font_item_note",
     "print.font_order_note",
+    "print.beep_on_ticket",
+    "print.beep_pattern",
 ]
 
 _PRINT_SETTING_DEFAULTS = {
@@ -80,6 +82,17 @@ _PRINT_SETTING_DEFAULTS = {
     "print.font_ingredient":   "0:0:0",
     "print.font_item_note":    "0:0:0",
     "print.font_order_note":   "0:1:0",
+    "print.beep_on_ticket":    "true",
+    "print.beep_pattern":      "double",
+}
+
+# Beep patterns: (n1=on×100ms, n2=off×100ms, n3=count)
+# Using ESC BEL n1 n2 n3 (0x1B 0x07 n1 n2 n3)
+_BEEP_PATTERNS = {
+    "single":  (2, 2, 1),   # one 200ms beep
+    "double":  (1, 1, 2),   # two short beeps
+    "triple":  (1, 1, 3),   # three short beeps
+    "long":    (5, 2, 1),   # one 500ms beep
 }
 
 # SIZE byte values (ESC ! base, no bold bit):
@@ -179,6 +192,21 @@ def is_spoof_mode() -> bool:
         db.close()
 
 
+def send_test_beep(ip: str, port: int, n1: int, n2: int, n3: int) -> Tuple[bool, str]:
+    """Send a standalone beep-only job. n1=on-time×100ms, n2=off-time×100ms, n3=count."""
+    if is_spoof_mode():
+        logger.info("Spoof printing ON — dropping test beep")
+        return True, ""
+    try:
+        p = _get_printer(ip, port)
+        p._raw(bytes([0x1b, 0x07, n1, n2, n3]))
+        p.close()
+        return True, ""
+    except Exception as e:
+        logger.error("Test beep failed for %s:%s — %s", ip, port, e)
+        return False, str(e)
+
+
 def send_test_print(ip: str, port: int, name: str) -> Tuple[bool, str]:
     if is_spoof_mode():
         logger.info("Spoof printing ON — dropping test print for %s", name)
@@ -563,6 +591,22 @@ def _print_kitchen_ticket(p: Network, order: Order, items: List[OrderItem], db:
         p._raw(b'\x1b\x21\x00')
 
     p._raw(b'\n\n\n')
+
+    # Beep before cut so the buzzer fires as the paper advances
+    beep_enabled = cfg.get("print.beep_on_ticket", "true") == "true"
+    if beep_enabled:
+        pattern = cfg.get("print.beep_pattern", "double")
+        if pattern.startswith("custom:"):
+            # custom:n1:n2:n3
+            try:
+                _, n1s, n2s, n3s = pattern.split(":")
+                beep_bytes = (int(n1s), int(n2s), int(n3s))
+            except (ValueError, TypeError):
+                beep_bytes = _BEEP_PATTERNS["double"]
+        else:
+            beep_bytes = _BEEP_PATTERNS.get(pattern, _BEEP_PATTERNS["double"])
+        p._raw(bytes([0x1b, 0x07, beep_bytes[0], beep_bytes[1], beep_bytes[2]]))
+
     p.cut()