feat: implement ntfy-discord bridge in Go

- SSE subscription to ntfy with auto-reconnect
- Discord webhook integration with embed formatting
- Priority to color mapping, tag to emoji conversion
- Native HashiCorp Vault support (Kubernetes + token auth)
- Hot reload secrets via fsnotify or Vault polling
- Prometheus metrics (/metrics endpoint)
- Health/ready endpoints for Kubernetes probes
- Comprehensive unit tests and fuzz tests
- Multi-stage Docker build (~10MB scratch image)
- CI/CD pipeline for Gitea Actions

Dockerfile

@@ -0,0 +1,33 @@
+# Build stage
+FROM golang:1.25-alpine AS builder
+
+WORKDIR /app
+
+# Install ca-certificates for HTTPS
+RUN apk add --no-cache ca-certificates
+
+# Copy go mod files
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Build static binary
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-w -s" -o /ntfy-discord .
+
+# 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 /ntfy-discord /ntfy-discord
+
+# Run as non-root
+USER 65534:65534
+
+EXPOSE 8080
+
+ENTRYPOINT ["/ntfy-discord"]