feat: custom voice support, CI pipeline, and Renovate config

- VoiceRegistry for trained voices from Kubeflow pipeline
- Custom voice routing in synthesize()
- NATS subjects for listing/refreshing voices
- pyproject.toml with ruff/pytest config
- Full test suite (26 tests)
- Gitea Actions CI (lint, test, docker, notify)
- Renovate config for automated dependency updates

Ref: ADR-0056, ADR-0057

renovate.json

@@ -0,0 +1,7 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>daviestechlabs/renovate-config",
+    "local>daviestechlabs/renovate-config:python"
+  ]
+}