fix: restore Makefile usage in build.yml and Dockerfile

Update CI and Docker build to use `make` instead of removed scripts/.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -17,4 +17,4 @@ jobs:
           go-version-file: go.mod
 
       - name: Build
-        run: scripts/build.sh --all
+        run: make build-all

Dockerfile

@@ -3,7 +3,7 @@
 # ============================================================
 FROM golang:1.25-alpine AS builder
 
-RUN apk add --no-cache git bash
+RUN apk add --no-cache git make
 
 WORKDIR /src
 
@@ -13,7 +13,7 @@ RUN go mod download
 
 # Copy source and build
 COPY . .
-RUN scripts/build.sh
+RUN make build
 
 # ============================================================
 # Stage 2: Minimal runtime image