engines: import f5-tts + kokoro + tortoise sidecars into the tree

The python FastAPI sidecars have lived ad-hoc at /srv/appdata/
<engine>/build/ on the host without version control. Bringing them into
the skald repo so the engine code travels with the cross-engine
routing it depends on.

This commit lands the VANILLA version of each engine on main:

  engines/f5-tts/    SWivid F5-TTS (CC-BY-NC weights flagged)
  engines/kokoro/    hexgrad Kokoro-82M (Apache 2.0 top to bottom)
  engines/tortoise/  neonbjb Tortoise-TTS (Apache 2.0 top to bottom)

Engine-specific kludges (question doubling, GPU coordination,
pause-duration tuning) get layered on engine/* branches per the
README. Main stays the safe-to-read baseline.

engines/kokoro/compose.yml

@@ -0,0 +1,37 @@
+# Kokoro-82M TTS stack on the host.
+#
+# Audiobook-quality narrator engine (Apache 2.0 code + weights —
+# clean stack vs F5-TTS's CC-BY-NC asterisk). Sibling to f5-tts;
+# both share /srv/appdata/f5-tts/audio so skald's audio
+# route serves outputs from either engine through the same path.
+#
+# License: Apache 2.0 top to bottom. Right for share/publish.
+name: kokoro
+
+services:
+  kokoro:
+    image: registry.example.local:5000/kokoro:0.5
+    container_name: kokoro
+    restart: unless-stopped
+    deploy:
+      resources:
+        reservations:
+          devices:
+            - driver: nvidia
+              count: all
+              capabilities: [gpu]
+    ports:
+      - "127.0.0.1:7794:7860"
+      - "127.0.0.1:7794:7860"
+    volumes:
+      - /srv/appdata/kokoro/hf-cache:/cache/hf
+      # Shared with f5-tts so skald's /audio route covers both.
+      - /srv/appdata/f5-tts/audio:/audio
+    environment:
+      HF_HOME: /cache/hf
+      HF_HUB_DISABLE_TELEMETRY: "1"
+    labels:
+      org.sulkta.domain: "sulkta"
+      org.sulkta.owner: "Sulkta"
+      org.sulkta.managed-by: "compose"
+      org.sulkta.role: "kokoro"