ci: add Gitea Actions workflow for make check (#21)

Adds CI workflow that runs `make check` on push/PR to main.

Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: clawbot <clawbot@eeqj.de>
Reviewed-on: #21
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>
Co-committed-by: clawbot <sneak+clawbot@sneak.cloud>

Dockerfile

@@ -1,50 +1,46 @@
-# Build stage
-FROM golang:1.24-alpine AS builder
+# Lint stage — fast feedback on formatting and lint issues
+# golangci/golangci-lint v2.1.6 (2026-03-10)
+FROM golangci/golangci-lint@sha256:568ee1c1c53493575fa9494e280e579ac9ca865787bafe4df3023ae59ecf299b AS lint
 
-# Install build dependencies
-RUN apk add --no-cache \
-    gcc \
-    musl-dev \
-    make \
-    git
-
-# Set working directory
-WORKDIR /build
-
-# Copy go mod files
+WORKDIR /src
 COPY go.mod go.sum ./
-
-# Download dependencies
 RUN go mod download
 
-# Copy source code
 COPY . .
 
-# Build the binary
-RUN CGO_ENABLED=1 go build -v -o secret cmd/secret/main.go
+RUN make fmt-check
+RUN make lint
+
+# Build stage — tests and compilation
+# golang 1.24.13-alpine (2026-03-10)
+FROM golang@sha256:8bee1901f1e530bfb4a7850aa7a479d17ae3a18beb6e09064ed54cfd245b7191 AS builder
+
+# Force BuildKit to run the lint stage
+COPY --from=lint /src/go.sum /dev/null
+
+RUN apk add --no-cache gcc musl-dev make git gnupg
+
+WORKDIR /build
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+RUN make test
+RUN make build
 
 # Runtime stage
-FROM alpine:latest
+# alpine 3.23 (2026-03-10)
+FROM alpine@sha256:25109184c71bdad752c8312a8623239686a9a2071e8825f20acb8f2198c3f659
 
-# Install runtime dependencies
-RUN apk add --no-cache \
-    ca-certificates \
-    gnupg
+RUN apk add --no-cache ca-certificates gnupg
 
-# Create non-root user
 RUN adduser -D -s /bin/sh secret
 
-# Copy binary from builder
 COPY --from=builder /build/secret /usr/local/bin/secret
-
-# Ensure binary is executable
 RUN chmod +x /usr/local/bin/secret
 
-# Switch to non-root user
 USER secret
-
-# Set working directory
 WORKDIR /home/secret
 
-# Set entrypoint
-ENTRYPOINT ["secret"]
+ENTRYPOINT ["secret"]