feat(p1): complete P1 foundation stage

- monorepo: pnpm workspace + go.work + pyproject.toml + commitlint/husky
- infra: docker-compose (minimal + full profiles) + init-sql + prometheus
- arch-scan: multi-language scanner skeleton (TS/Go/Python/Proto)
- shared-proto: buf v2 + classes.proto (ClassService CRUD contract)
- api-gateway: Go/Gin + JWT HS256 auth + reverse proxy + request ID
- classes: NestJS golden template (error system + observability + middleware + CRUD + tests)
- teacher-portal: Next.js + paper-feel UI design system
- CI/CD: 4 workflows (go/ts/py/proto)
- docs: migration guide + project_rules + coding-standards + git-workflow + ui-design-system + 004 + 9 module READMEs + known-issues + spec/plan migration + roadmap

services/api-gateway/Dockerfile

@@ -0,0 +1,15 @@
+# Build stage
+FROM golang:1.22-alpine AS builder
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -o api-gateway .
+
+# Runtime stage
+FROM alpine:3.20
+RUN apk --no-cache add ca-certificates
+WORKDIR /app
+COPY --from=builder /app/api-gateway .
+EXPOSE 8080
+CMD ["./api-gateway"]