feat: initial commit — backend API + student cabinet frontend

- Go backend: auth (JWT), points earn/spend, QR token generation,
  partners, admin grant/stats endpoints with chi router
- Next.js 14 frontend: login, student dashboard, transaction history,
  QR display, partners list
- PostgreSQL migrations (4 tables), Redis cache, Docker Compose
- CORS middleware, role-based route protection, Zustand auth store

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

backend/pkg/cache/redis.go

@@ -0,0 +1,23 @@
+// Package cache provides Redis client initialization.
+package cache
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// NewClient creates and validates a Redis client using the given REDIS_URL.
+// Returns an error if the URL cannot be parsed or if the initial PING fails.
+func NewClient(ctx context.Context, redisURL string) (*redis.Client, error) {
+	opts, err := redis.ParseURL(redisURL)
+	if err != nil {
+		return nil, fmt.Errorf("cache.NewClient: parse URL: %w", err)
+	}
+	client := redis.NewClient(opts)
+	if err := client.Ping(ctx).Err(); err != nil {
+		return nil, fmt.Errorf("cache.NewClient: ping: %w", err)
+	}
+	return client, nil
+}

backend/pkg/db/postgres.go

@@ -0,0 +1,22 @@
+// Package db provides PostgreSQL connection pool initialization.
+package db
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// NewPool creates and validates a pgx connection pool using the given DATABASE_URL.
+// Returns an error if the pool cannot be created or if the initial ping fails.
+func NewPool(ctx context.Context, databaseURL string) (*pgxpool.Pool, error) {
+	pool, err := pgxpool.New(ctx, databaseURL)
+	if err != nil {
+		return nil, fmt.Errorf("db.NewPool: create pool: %w", err)
+	}
+	if err := pool.Ping(ctx); err != nil {
+		return nil, fmt.Errorf("db.NewPool: ping: %w", err)
+	}
+	return pool, nil
+}

backend/pkg/response/json.go

@@ -0,0 +1,32 @@
+// Package response provides helpers for writing consistent JSON API responses.
+// Every handler must use these helpers — never call json.Encode directly.
+package response
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+type successBody struct {
+	Data interface{} `json:"data"`
+}
+
+type errorBody struct {
+	Error string `json:"error"`
+}
+
+// JSON writes a successful JSON response with the given HTTP status code and data payload.
+// The payload is wrapped in {"data": ...} to match the API envelope convention.
+func JSON(w http.ResponseWriter, status int, data interface{}) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(successBody{Data: data}) //nolint:errcheck
+}
+
+// Error writes a JSON error response with the given HTTP status code and human-readable message.
+// The message is wrapped in {"error": ...}.
+func Error(w http.ResponseWriter, status int, message string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(errorBody{Error: message}) //nolint:errcheck
+}