feat(voice): bundled Vietnamese voice calls (master + player)

Speak the called number on master draw, "Chờ N" when a row is one
away, and "Kinh" on bingo. No runtime TTS API — clips are
pre-generated by `scripts/generate-audio.py` (free edge-tts) and
shipped as static MP3s under `static/audio/{voiceId}/`.

- src/lib/vietnamese-number.js + test (40 cases): tonal exceptions
  mười lăm / hai mươi mốt / hai mươi lăm
- src/lib/voice.js: lazy <audio> cache, token-based cancellation,
  cho+number sequencer, on-unmount cleanup
- src/lib/audio-manifest.js: re-exports static/audio/manifest.json
- scripts/generate-audio.py: discovers every vi-* edge-tts voice,
  writes 92 clips per voice + manifest.json
- static/audio/manifest.json: placeholder until user runs the script
- src/lib/settings-store: +voiceEnabledMaster/voiceEnabledPlayer/voice
  with per-key validators
- src/lib/SettingsButton: new "Âm thanh" fieldset (toggles + voice
  picker rendered from manifest)
- MasterPanel.handleDrawNext: playNumber(next) + cancel on new game
- PlayerBoard $effect: playWaiting/playBingo beside toast/popup;
  cancel on regenerate / clear

To materialize the MP3s on first install:
    pip install edge-tts
    python3 scripts/generate-audio.py

Tests: 98 pass (40 number + 31 settings + 27 game-logic).

web/scripts/generate-audio.py

@@ -0,0 +1,111 @@
+#!/usr/bin/env python3
+"""Generate Vietnamese audio clips (1-90 + Chờ + Kinh) for every edge-tts
+Vietnamese voice. Output written to static/audio/{voiceId}/ and shipped
+with the app — runtime never calls TTS.
+
+Run once on a dev machine:
+
+    pip install edge-tts
+    python3 scripts/generate-audio.py
+"""
+import asyncio
+import json
+import os
+import re
+import sys
+
+OUT_ROOT = os.path.join(os.path.dirname(__file__), "..", "static", "audio")
+
+ONES = [
+    "không", "một", "hai", "ba", "bốn",
+    "năm", "sáu", "bảy", "tám", "chín",
+]
+
+
+def number_to_vietnamese(n: int) -> str:
+    """Mirror of src/lib/vietnamese-number.js for build-time use."""
+    if n < 10:
+        return ONES[n]
+    if n == 10:
+        return "mười"
+    if n < 20:
+        u = n - 10
+        return "mười lăm" if u == 5 else f"mười {ONES[u]}"
+    t, u = divmod(n, 10)
+    tens = f"{ONES[t]} mươi"
+    if u == 0:
+        return tens
+    if u == 1:
+        return f"{tens} mốt"
+    if u == 5:
+        return f"{tens} lăm"
+    return f"{tens} {ONES[u]}"
+
+
+def voice_id(short_name: str) -> str:
+    """vi-VN-HoaiMyNeural -> hoai-my"""
+    name = short_name.split("-")[-1]                 # HoaiMyNeural
+    name = re.sub(r"Neural$", "", name)              # HoaiMy
+    name = re.sub(r"(?<!^)(?=[A-Z])", "-", name)     # Hoai-My
+    return name.lower()                              # hoai-my
+
+
+def display_label(short_name: str, gender: str) -> str:
+    given = re.sub(r"Neural$", "", short_name.split("-")[-1])
+    given = re.sub(r"(?<!^)(?=[A-Z])", " ", given).strip()
+    gender_vi = "nữ" if gender.lower() == "female" else "nam"
+    return f"{given} ({gender_vi})"
+
+
+async def synth(text: str, voice: str, out: str) -> None:
+    import edge_tts
+    await edge_tts.Communicate(text, voice).save(out)
+    print(f"  {out}  ←  \"{text}\"")
+
+
+async def main() -> None:
+    import edge_tts
+    all_voices = await edge_tts.list_voices()
+    vi_voices = [v for v in all_voices if v["Locale"].startswith("vi-")]
+    if not vi_voices:
+        sys.exit("No Vietnamese voices found in edge-tts.")
+
+    seen_ids: set[str] = set()
+    manifest = {"voices": []}
+
+    for v in vi_voices:
+        vid = voice_id(v["ShortName"])
+        if vid in seen_ids:
+            sys.exit(f"Voice id collision: {vid} (from {v['ShortName']})")
+        seen_ids.add(vid)
+
+        out_dir = os.path.join(OUT_ROOT, vid)
+        os.makedirs(out_dir, exist_ok=True)
+        print(f"\n→ {v['ShortName']}  →  static/audio/{vid}/")
+
+        tasks = [
+            synth(number_to_vietnamese(n), v["ShortName"], os.path.join(out_dir, f"{n}.mp3"))
+            for n in range(1, 91)
+        ]
+        tasks.append(synth("Chờ",  v["ShortName"], os.path.join(out_dir, "cho.mp3")))
+        tasks.append(synth("Kinh", v["ShortName"], os.path.join(out_dir, "kinh.mp3")))
+        await asyncio.gather(*tasks)
+
+        manifest["voices"].append({
+            "id": vid,
+            "edgeName": v["ShortName"],
+            "label": display_label(v["ShortName"], v["Gender"]),
+            "gender": v["Gender"].lower(),
+        })
+
+    manifest_path = os.path.join(OUT_ROOT, "manifest.json")
+    with open(manifest_path, "w", encoding="utf-8") as f:
+        json.dump(manifest, f, ensure_ascii=False, indent=2)
+    print(f"\nWrote manifest with {len(manifest['voices'])} voice(s) → {manifest_path}")
+
+
+if __name__ == "__main__":
+    try:
+        asyncio.run(main())
+    except ImportError:
+        sys.exit("Install dep first: pip install edge-tts")