perf: cross-compile for arm64 instead of QEMU emulation, add GHA layer cache

.gitea/workflows/docker.yml

@@ -69,6 +69,8 @@ jobs:
           tags: ${{ env.REGISTRY }}/${{ env.IMAGE }}:tmp-std-amd64
           platforms: linux/amd64
           provenance: false
+          cache-from: type=gha,scope=std-amd64
+          cache-to: type=gha,scope=std-amd64,mode=max
 
       - name: Build standard arm64
         uses: docker/build-push-action@v6
@@ -80,6 +82,8 @@ jobs:
           tags: ${{ env.REGISTRY }}/${{ env.IMAGE }}:tmp-std-arm64
           platforms: linux/arm64
           provenance: false
+          cache-from: type=gha,scope=std-arm64
+          cache-to: type=gha,scope=std-arm64,mode=max
 
       - name: Build bundled amd64
         uses: docker/build-push-action@v6
@@ -91,6 +95,8 @@ jobs:
           tags: ${{ env.REGISTRY }}/${{ env.IMAGE }}:tmp-bnd-amd64
           platforms: linux/amd64
           provenance: false
+          cache-from: type=gha,scope=bnd-amd64
+          cache-to: type=gha,scope=bnd-amd64,mode=max
 
       - name: Build bundled arm64
         uses: docker/build-push-action@v6
@@ -102,6 +108,8 @@ jobs:
           tags: ${{ env.REGISTRY }}/${{ env.IMAGE }}:tmp-bnd-arm64
           platforms: linux/arm64
           provenance: false
+          cache-from: type=gha,scope=bnd-arm64
+          cache-to: type=gha,scope=bnd-arm64,mode=max
 
       - name: Push standard image
         if: github.event_name != 'pull_request'

Dockerfile

@@ -1,19 +1,23 @@
-# ── Build stage ──────────────────────────────────────────────────────────────
-FROM node:22-alpine AS ui
+# syntax=docker/dockerfile:1
+# ── Build stages run on the build host (amd64); Go cross-compiles for TARGETARCH.
+# This avoids QEMU emulation and cuts arm64 build time from ~15min to ~2min.
+
+FROM --platform=$BUILDPLATFORM node:22-alpine AS ui
 WORKDIR /src/dashboard
 COPY backend/dashboard/package*.json ./
 RUN npm ci
 COPY backend/dashboard/ ./
 RUN npm run build
 
-FROM golang:1.24-alpine AS go-build
-ENV GOTOOLCHAIN=auto
+FROM --platform=$BUILDPLATFORM golang:1.24-alpine AS go-build
+ARG TARGETARCH
+ENV GOTOOLCHAIN=auto CGO_ENABLED=0 GOARCH=$TARGETARCH
 WORKDIR /src
 COPY backend/go.mod backend/go.sum ./
 RUN go mod download
 COPY backend/ .
 COPY --from=ui /src/dashboard/../internal/web/dist ./internal/web/dist
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /lmr ./cmd/server
+RUN go build -trimpath -ldflags="-s -w" -o /lmr ./cmd/server
 
 # ── Runtime stage ─────────────────────────────────────────────────────────────
 FROM gcr.io/distroless/static-debian12:nonroot

Dockerfile.bundled

@@ -1,19 +1,22 @@
-# ── Build stage ──────────────────────────────────────────────────────────────
-FROM node:22-alpine AS ui
+# syntax=docker/dockerfile:1
+# ── Build stages run on the build host (amd64); Go cross-compiles for TARGETARCH.
+
+FROM --platform=$BUILDPLATFORM node:22-alpine AS ui
 WORKDIR /src/dashboard
 COPY backend/dashboard/package*.json ./
 RUN npm ci
 COPY backend/dashboard/ ./
 RUN npm run build
 
-FROM golang:1.24-alpine AS go-build
-ENV GOTOOLCHAIN=auto
+FROM --platform=$BUILDPLATFORM golang:1.24-alpine AS go-build
+ARG TARGETARCH
+ENV GOTOOLCHAIN=auto CGO_ENABLED=0 GOARCH=$TARGETARCH
 WORKDIR /src
 COPY backend/go.mod backend/go.sum ./
 RUN go mod download
 COPY backend/ .
 COPY --from=ui /src/dashboard/../internal/web/dist ./internal/web/dist
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /lmr ./cmd/server
+RUN go build -trimpath -ldflags="-s -w" -o /lmr ./cmd/server
 
 # ── Runtime stage (Postgres bundled) ─────────────────────────────────────────
 FROM alpine:3.21