🐛 fix: Move WORKDIR before COPY in Dockerfile.build

docker/Dockerfile.build

@@ -32,12 +32,12 @@ RUN go install github.com/swaggo/swag/cmd/swag@latest && \
     go install golang.org/x/tools/cmd/goimports@latest && \
     go install honnef.co/go/tools/cmd/staticcheck@latest
 
+# Simple build environment - source code is mounted at runtime
+WORKDIR /build
+
 # Copy only go.mod and go.sum first for dependency caching
 COPY go.mod go.sum ./
 RUN go mod download && go mod verify
 
-# Simple build environment - source code is mounted at runtime
-WORKDIR /build
-
 # Pre-download common Go tools (already installed in base)
 # RUN go install github.com/swaggo/swag/cmd/swag@latest