ci: merge test+build+push into single pipeline

- Single job: vet → test → build binary → build image → push
- Image build/push only on main push (skip on PR)
- Fixed Dockerfile: golang:1.26, build cmd/worker, removed HTTP healthcheck
- Removed separate build-push.yml

Dockerfile

@@ -1,22 +1,20 @@
-FROM golang:1.21-alpine as builder
+FROM golang:1.26-alpine AS builder
 
 WORKDIR /app
 COPY go.mod go.sum ./
 RUN go mod download
-
 COPY . .
-RUN CGO_ENABLED=0 GOOS=linux go build -o workflows ./cmd/poimen/main.go
 
-FROM alpine:latest
+# Re-use CI-built binary if present, otherwise build
+ARG BINARY_PATH=
+RUN if [ -n "$BINARY_PATH" ] && [ -f "$BINARY_PATH" ]; then \
+      cp "$BINARY_PATH" worker; \
+    else \
+      CGO_ENABLED=0 GOOS=linux go build -o worker ./cmd/worker; \
+    fi
 
+FROM alpine:3.20
 RUN apk --no-cache add ca-certificates
-
 WORKDIR /app
-COPY --from=builder /app/workflows .
-
-EXPOSE 8080
-
-HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=3 \
-  CMD wget --no-verbose --tries=1 --spider http://localhost:8080/health || exit 1
-
-ENTRYPOINT ["./workflows"]
+COPY --from=builder /app/worker .
+ENTRYPOINT ["./worker"]