feat(homepage): split AI fleet into role-based groups on a dedicated AI tab

Move the ~22-service flat "AI Systems" group off the Main tab into a new
four-tab layout (Main / AI / Infrastructure / Toolchain). The AI tab sorts
the inference fleet by function into seven groups:

  AI - Inference        gen, char-rp, char-rp-reasoning, Granite summarizer
  AI - Eval & Retrieval Selene, Skywork Reward, Qwen3 rerank/embed, image-bench
  AI - Gateways & Chat  LiteLLM, Asset Engine, Gateway Chat, Open WebUI, ...
  AI - Speech (TTS)     Chatterbox Fast, Kokoro, mOrpheus
  AI - Audio Tools      Parakeet ASR, YT Voice Clipper
  AI - Image & Media    ComfyUI, Arbo
  AI - Dormant          stopped rollback seats + retired auditions

Relabel each stack's homepage.group so canonical stacks/ matches the live
containers on ana-ml2, ana-docker, and irv-ml1. Dormant stacks were refreshed
with `docker compose up --no-start` so they carry the new label while staying
stopped (compose-start rollback preserved). settings.yaml drives tab/order/
columns; services.yaml and README updated to the new scheme.

stacks/parakeet/compose.yaml

@@ -46,7 +46,7 @@ services:
       # First boot may include a ~400 MB model download.
       start_period: 300s
     labels:
-      - homepage.group=AI Systems
+      - homepage.group=AI - Audio Tools
       - homepage.name=Parakeet ASR
       - homepage.icon=mdi-microphone
       - homepage.description=Parakeet-TDT speech-to-text via sherpa-onnx (irv-ml1)