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/parakeet/compose.yaml

@@ -38,7 +38,8 @@ services:
     volumes:
       - ${PARAKEET_MODELS_DIR}:/models
     healthcheck:
-      test: ["CMD-SHELL", "curl -fsS http://localhost:8000/healthz >/dev/null || exit 1"]
+      # Image ships wget (apt) but not curl — use wget so the check actually runs.
+      test: ["CMD-SHELL", "wget -q -O /dev/null http://localhost:8000/healthz || exit 1"]
       interval: 30s
       timeout: 10s
       retries: 3