feat(api): API keys + Redis rate limiting + usage stats

Add an optional API-key layer to the public read-only API. Keys grant
higher per-minute rate limits and attribute usage; anonymous callers are
still allowed at a lower IP-based budget.

- migration 0008_api_key: api_key table (sha256 hash only, plaintext shown once)
- apikey pkg: key generation + hashing
- ratelimit pkg: Redis fixed-window limiter + per-key usage counters; fails open
- public API middleware: X-API-Key / Bearer auth, X-RateLimit-* headers, 429+Retry-After
- admin: issue/list/revoke keys + usage view (API + UI tab)

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

api/internal/handler/middleware_db_test.go

@@ -0,0 +1,120 @@
+package handler
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/baicai2026-baicai/goods/api/internal/apikey"
+	"github.com/baicai2026-baicai/goods/api/internal/ratelimit"
+	"github.com/baicai2026-baicai/goods/api/internal/store"
+)
+
+// newRateLimitedHandler builds a handler backed by the test DB and a live Redis
+// limiter, plus a freshly issued API key with the given per-minute limit. It
+// skips when either backend is unavailable.
+func newRateLimitedHandler(t *testing.T, keyLimit int) (h *Handler, plaintextKey string) {
+	t.Helper()
+	dsn := os.Getenv("OPENGOODS_DATABASE_URL")
+	if dsn == "" {
+		dsn = "postgres://opengoods:opengoods@localhost:5432/opengoods?sslmode=disable"
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	pool, err := pgxpool.New(ctx, dsn)
+	if err != nil {
+		t.Skipf("no database: %v", err)
+	}
+	if err := pool.Ping(ctx); err != nil {
+		pool.Close()
+		t.Skipf("database not reachable: %v", err)
+	}
+	var hasTable bool
+	if err := pool.QueryRow(ctx, "SELECT to_regclass('public.api_key') IS NOT NULL").Scan(&hasTable); err != nil || !hasTable {
+		pool.Close()
+		t.Skip("migrations not applied (api_key missing)")
+	}
+
+	redisURL := os.Getenv("OPENGOODS_REDIS_URL")
+	if redisURL == "" {
+		redisURL = "redis://localhost:6379/0"
+	}
+	limiter := ratelimit.New(redisURL)
+	pingCtx, pingCancel := context.WithTimeout(context.Background(), time.Second)
+	defer pingCancel()
+	if err := limiter.Ping(pingCtx); err != nil {
+		pool.Close()
+		t.Skipf("redis not reachable: %v", err)
+	}
+
+	key, hash, prefix, err := apikey.Generate()
+	if err != nil {
+		pool.Close()
+		t.Fatal(err)
+	}
+	name := fmt.Sprintf("test-key-%d", time.Now().UnixNano())
+	if _, err := pool.Exec(context.Background(),
+		`INSERT INTO api_key (name, key_prefix, key_hash, rate_limit_per_min) VALUES ($1,$2,$3,$4)`,
+		name, prefix, hash, keyLimit); err != nil {
+		pool.Close()
+		t.Fatalf("insert api_key: %v", err)
+	}
+	t.Cleanup(func() {
+		_, _ = pool.Exec(context.Background(), "DELETE FROM api_key WHERE key_hash=$1", hash)
+		pool.Close()
+	})
+
+	return New(store.New(pool), nil).WithRateLimit(limiter, 60), key
+}
+
+func TestRateLimitHeadersAndKeyAuth(t *testing.T) {
+	h, key := newRateLimitedHandler(t, 100)
+	req := httptest.NewRequest(http.MethodGet, "/api/"+APIVersion+"/categories", nil)
+	req.Header.Set("X-API-Key", key)
+	rec := httptest.NewRecorder()
+	h.Router().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, body = %s", rec.Code, rec.Body.String())
+	}
+	if got := rec.Header().Get("X-RateLimit-Limit"); got != "100" {
+		t.Fatalf("X-RateLimit-Limit = %q, want 100 (key limit)", got)
+	}
+	if rec.Header().Get("X-RateLimit-Remaining") == "" {
+		t.Fatal("missing X-RateLimit-Remaining header")
+	}
+}
+
+func TestInvalidKeyRejected(t *testing.T) {
+	h, _ := newRateLimitedHandler(t, 100)
+	req := httptest.NewRequest(http.MethodGet, "/api/"+APIVersion+"/categories", nil)
+	req.Header.Set("X-API-Key", "og_live_thiskeydoesnotexist123456")
+	rec := httptest.NewRecorder()
+	h.Router().ServeHTTP(rec, req)
+	if rec.Code != http.StatusUnauthorized {
+		t.Fatalf("status = %d, want 401; body = %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestRateLimitExceeded(t *testing.T) {
+	h, key := newRateLimitedHandler(t, 1)
+	do := func() int {
+		req := httptest.NewRequest(http.MethodGet, "/api/"+APIVersion+"/categories", nil)
+		req.Header.Set("X-API-Key", key)
+		rec := httptest.NewRecorder()
+		h.Router().ServeHTTP(rec, req)
+		return rec.Code
+	}
+	if code := do(); code != http.StatusOK {
+		t.Fatalf("first request status = %d, want 200", code)
+	}
+	if code := do(); code != http.StatusTooManyRequests {
+		t.Fatalf("second request status = %d, want 429", code)
+	}
+}