feat: rewrite pipeline-bridge in Go

Replace Python implementation with Go for smaller container images.
Uses handler-base Go module for NATS, health, and telemetry.

- main.go: pipeline bridge with Argo/Kubeflow HTTP submission
- main_test.go: 8 tests covering helpers and HTTP submit functions
- Dockerfile: multi-stage golang:1.25-alpine → scratch
- CI: Gitea Actions with lint/test/release/docker/notify

Dockerfile

@@ -1,13 +1,31 @@
-# Pipeline Bridge - Using handler-base
-ARG BASE_TAG=latest
-FROM ghcr.io/billy-davies-2/handler-base:${BASE_TAG}
+# Build stage
+FROM golang:1.25-alpine AS builder
 
 WORKDIR /app
 
-# Install additional dependencies from pyproject.toml
-COPY pyproject.toml .
-RUN uv pip install --system --no-cache httpx kubernetes
+# Install ca-certificates for HTTPS
+RUN apk add --no-cache ca-certificates
 
-COPY pipeline_bridge.py .
+# Copy go mod files
+COPY go.mod go.sum ./
+RUN go mod download
 
-CMD ["python", "pipeline_bridge.py"]
+# Copy source code
+COPY . .
+
+# Build static binary
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-w -s" -o /pipeline-bridge .
+
+# 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 /pipeline-bridge /pipeline-bridge
+
+# Run as non-root
+USER 65534:65534
+
+ENTRYPOINT ["/pipeline-bridge"]