stacks: parakeet healthcheck (curl→wget); qwen3-tts variant labels

- parakeet/compose.yaml: healthcheck was using curl which isn't in the
  image (only wget is, via apt). 2,190 failing checks — switched to
  `wget -q -O /dev/null`, container went healthy on recreate.
- qwen3-tts/.env.example: variant annotation was reversed. The upstream
  wrapper's runtime error is unambiguous: voice cloning requires the
  -Base variant, not -CustomVoice. Corrected the comment block and
  flipped the default to Qwen/Qwen3-TTS-12Hz-1.7B-Base.
- qwen3-tts/README.md: 0.6B switch snippet now suffixes -Base too,
  since plain `Qwen/Qwen3-TTS-12Hz-0.6B` isn't published on HF.

stacks/qwen3-tts/README.md

@@ -95,7 +95,7 @@ If 1.7B is too heavy or you need to share GPUs more aggressively:
 ```bash
 ssh irv-ml1 '
   cd /opt/docker/compose/qwen3-tts && \
-  sed -i "s|^QWEN3_TTS_MODEL=.*|QWEN3_TTS_MODEL=Qwen/Qwen3-TTS-12Hz-0.6B|" .env && \
+  sed -i "s|^QWEN3_TTS_MODEL=.*|QWEN3_TTS_MODEL=Qwen/Qwen3-TTS-12Hz-0.6B-Base|" .env && \
   docker compose up -d
 '
 ```