feat: rewrite tts-module in Go

Replace Python streaming TTS service with Go for smaller container images.
- VoiceRegistry: discovers custom voices from model store
- NATS subscriptions: TTS requests, voice list, voice refresh
- JetStream AI_VOICE_TTS stream setup
- Chunked audio streaming over NATS
- Dockerfile: multi-stage golang:1.25-alpine → scratch
- CI: Gitea Actions with lint/test/release/docker/notify

Dockerfile

@@ -1,14 +1,31 @@
-FROM python:3.12-slim
+# Build stage
+FROM golang:1.25-alpine AS builder
 
 WORKDIR /app
 
-# Copy requirements and install dependencies
-COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+# Install ca-certificates for HTTPS
+RUN apk add --no-cache ca-certificates
 
-# Copy application code
-COPY tts_streaming.py .
-COPY healthcheck.py .
+# Copy go mod files
+COPY go.mod go.sum ./
+RUN go mod download
 
-# Run the service
-CMD ["python", "tts_streaming.py"]
+# Copy source code
+COPY . .
+
+# Build static binary
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-w -s" -o /tts-module .
+
+# Runtime stage - scratch for minimal image
+FROM scratch
+
+# Copy CA certificates for HTTPS
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+
+# Copy binary
+COPY --from=builder /tts-module /tts-module
+
+# Run as non-root
+USER 65534:65534
+
+ENTRYPOINT ["/tts-module"]