feat(voice): Pas 2 — install voice deps, vendor discord-ext-voice-recv, setup assets

Foundation pentru Discord voice-to-voice pipeline.

- requirements.txt: faster-whisper, silero-vad, num2words, numpy, PyNaCl
- vendor/discord-ext-voice-recv/: vendored la commit ac04ea7b09 (bump version
  0.5.3a) — Discord voice protocol fragil, upstream hobby fork. Adapter layer
  in src/voice/_discord_voice_adapter.py izolează churn (swap la py-cord =
  doar acel fișier rescris). VENDOR_INFO.md documentează update procedure.
- tools/voice_setup.py: idempotent setup script — libopus check, ffmpeg
  check, Supertonic reachable, faster-whisper/silero-vad warm, assets
  generation. Exit 0 = green, 1 = needs human (currently libopus missing
  needs `sudo apt install -y libopus0`).
- assets/voice/: thinking.wav (filler "Stai puțin să-mi adun gândurile",
  ~2.8s), mhm.wav (listener noise), beep_200ms.wav (wake-up tone 880Hz).
- src/voice/__init__.py: package stub.

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

vendor/discord-ext-voice-recv/LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2015-present Imayhaveborkedit
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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+DEALINGS IN THE SOFTWARE.