feat: Initialize Go backend architecture with clean project structure

services/api/.golangci-lint.yml

@@ -0,0 +1,13 @@
+run:
+  timeout: 5m
+
+linters:
+  enable:
+    - govet
+    - revive
+    - staticcheck
+    - errcheck
+    - ineffassign
+
+issues:
+  exclude-use-default: false

services/api/Dockerfile

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+# Builder
+FROM golang:1.22-alpine AS builder
+WORKDIR /app
+COPY . .
+RUN go mod tidy
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o server ./cmd/server
+
+# Runtime
+FROM gcr.io/distroless/base-debian12
+COPY --from=builder /app/server /server
+EXPOSE 8080
+ENTRYPOINT ["/server"]

services/api/Makefile

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+BINARY=server
+
+build:
+	go build -o bin/$(BINARY) ./cmd/server
+
+run:
+	go run ./cmd/server
+
+test:
+	go test ./...
+
+fmt:
+	go fmt ./...
+
+lint:
+	golangci-lint run

services/api/README.md

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+# Nester API
+
+Production-grade Go backend service with clean architecture foundations.
+
+## Overview
+
+The Nester backend is transitioning from Node.js/Express to Go to support long-term scalability and align with ecosystem standards. This service serves as the authoritative API layer for vault, user, and offramp domains.
+
+## Directory Structure
+
+### `cmd/`
+**Entrypoints only.** Contains `server/main.go` — application bootstrap and port resolution. No domain logic here.
+
+### `internal/`
+**Private domain logic.** Not importable by external packages.
+
+- `config/` — configuration loading and validation
+- `domain/` — domain entities and business logic
+  - `vault/` — vault operations and state
+  - `user/` — user identity and auth
+  - `offramp/` — off-ramp transaction processing
+- `handler/` — HTTP request handlers
+- `middleware/` — request/response middleware
+- `repository/` — data access layer
+- `service/` — business logic orchestration
+
+### `pkg/`
+**Reusable utilities.** Importable by external packages.
+
+- `response/` — standard HTTP response formatting
+- `validator/` — input validation helpers
+
+### `migrations/`
+**Database schema evolution.** Version-controlled SQL or Go migration scripts.
+
+## Local Development
+
+### Prerequisites
+- Go 1.22+
+- golangci-lint (optional, for linting)
+
+### Running the server
+
+```bash
+make run
+```
+
+Server starts on `http://localhost:8080` (or `$PORT` if set).
+
+### Health check
+
+```bash
+curl http://localhost:8080/healthz
+# Returns: ok (200)
+```
+
+### Building
+
+```bash
+make build
+```
+
+Binary written to `bin/server`.
+
+### Testing
+
+```bash
+make test
+```
+
+### Code quality
+
+Format code:
+```bash
+make fmt
+```
+
+Lint:
+```bash
+make lint
+```
+
+## Docker
+
+### Build
+
+```bash
+docker build -t nester-api .
+```
+
+Multi-stage build ensures minimal runtime image (~15MB).
+
+### Run
+
+```bash
+docker run -p 8080:8080 nester-api
+```
+
+Set port with environment variable:
+```bash
+docker run -p 9000:9000 -e PORT=9000 nester-api
+```
+
+## Architecture Philosophy
+
+**Clean Architecture.** Domain logic is isolated from HTTP, database, and framework concerns. Changes to the web layer do not cascade into domain code.
+
+**Domain Isolation.** `internal/domain/*` packages own their boundaries. Cross-domain dependencies flow only through service/handler layers.
+
+**Minimal Abstraction.** Uses `net/http` directly instead of frameworks. Avoids premature indirection. Repository pattern introduced only where data access is complex.
+
+**Simplicity First.** No dependency injection containers, no global singletons, no reflection-based magic. Code is explicit and traceable.
+
+## Future Phases
+
+1. **Database layer** — PostgreSQL integration via `internal/repository`
+2. **Auth middleware** — JWT validation in `internal/middleware`
+3. **Vault domain** — Core business logic in `internal/domain/vault`
+4. **API v1** — Public endpoints in `internal/handler`
+5. **Integration tests** — End-to-end validation
+
+---
+
+*Go version: 1.22+*
+*Module: github.com/Suncrest-Labs/nester*

services/api/cmd/server/main.go

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+package main
+
+import (
+	"log"
+	"net/http"
+	"os"
+)
+
+func main() {
+	port := resolvePort()
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/healthz", healthHandler)
+
+	server := &http.Server{
+		Addr:    ":" + port,
+		Handler: mux,
+	}
+
+	log.Printf("server starting on :%s", port)
+
+	if err := server.ListenAndServe(); err != nil {
+		log.Fatalf("server failed: %v", err)
+	}
+}
+
+func resolvePort() string {
+	if p := os.Getenv("PORT"); p != "" {
+		return p
+	}
+	return "8080"
+}
+
+func healthHandler(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write([]byte("ok"))
+}

services/api/go.mod

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+module github.com/Suncrest-Labs/nester
+
+go 1.22