feat(voice-client): PySide6 desktop client and Windows build scripts

Add voice_confirmation_client (poll, TTS MP3 playback, mic WAV resolve),
PyInstaller spec, start/build helpers, and API unit tests.

Pending manual testing: end-to-end on OR workstations and packaged exe.

Made-with: Cursor

voice_confirmation_client/core/paths.py

@@ -0,0 +1,47 @@
+"""Resolve bundled helper binaries (ffplay/ffmpeg) next to the package or PyInstaller extract dir."""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+
+def package_root() -> Path:
+    """Directory containing `voice_confirmation_client` package."""
+    return Path(__file__).resolve().parent.parent
+
+
+def frozen_base() -> Path | None:
+    """PyInstaller onefile/onedir: sys._MEIPASS or executable dir."""
+    if getattr(sys, "frozen", False):
+        meipass = getattr(sys, "_MEIPASS", None)
+        if meipass:
+            return Path(meipass)
+        return Path(sys.executable).resolve().parent
+    return None
+
+
+def bin_dir() -> Path:
+    """Optional `bin/` next to package (dev) or under _MEIPASS (frozen)."""
+    fb = frozen_base()
+    if fb is not None:
+        d = fb / "voice_confirmation_bin"
+        if d.is_dir():
+            return d
+    return package_root() / "bin"
+
+
+def find_ffplay() -> Path | None:
+    for name in ("ffplay", "ffplay.exe"):
+        p = bin_dir() / name
+        if p.is_file():
+            return p
+    return None
+
+
+def find_ffmpeg() -> Path | None:
+    for name in ("ffmpeg", "ffmpeg.exe"):
+        p = bin_dir() / name
+        if p.is_file():
+            return p
+    return None