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/adminstore/apikey.go

@@ -0,0 +1,130 @@
+package adminstore
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgconn"
+
+	"github.com/baicai2026-baicai/goods/api/internal/apikey"
+)
+
+// APIKeyRow is an admin-facing view of an issued API key (never the secret).
+type APIKeyRow struct {
+	ID              string  `json:"id"`
+	Name            string  `json:"name"`
+	KeyPrefix       string  `json:"key_prefix"`
+	OwnerEmail      *string `json:"owner_email"`
+	Tier            string  `json:"tier"`
+	RateLimitPerMin int     `json:"rate_limit_per_min"`
+	RevokedAt       *string `json:"revoked_at"`
+	CreatedBy       *string `json:"created_by"`
+	CreatedAt       string  `json:"created_at"`
+}
+
+// APIKeyInput holds the fields accepted when issuing a key.
+type APIKeyInput struct {
+	Name            string `json:"name"`
+	OwnerEmail      string `json:"owner_email"`
+	Tier            string `json:"tier"`
+	RateLimitPerMin int    `json:"rate_limit_per_min"`
+}
+
+// CreateAPIKey issues a new key, returning the one-time plaintext alongside the
+// stored row. Only the SHA-256 hash and a short display prefix are persisted.
+func (s *Store) CreateAPIKey(ctx context.Context, in APIKeyInput, createdBy string) (plaintext string, row APIKeyRow, err error) {
+	tier := in.Tier
+	if tier == "" {
+		tier = "free"
+	}
+	rate := in.RateLimitPerMin
+	if rate <= 0 {
+		rate = 120
+	}
+	var owner *string
+	if e := strings.TrimSpace(in.OwnerEmail); e != "" {
+		owner = &e
+	}
+
+	key, hash, prefix, err := apikey.Generate()
+	if err != nil {
+		return "", row, err
+	}
+
+	var revoked, created *time.Time
+	var createdByOut *string
+	err = s.pool.QueryRow(ctx, `
+INSERT INTO api_key (name, key_prefix, key_hash, owner_email, tier, rate_limit_per_min, created_by)
+VALUES ($1, $2, $3, $4, $5, $6, $7)
+RETURNING id, name, key_prefix, owner_email, tier, rate_limit_per_min, revoked_at, created_by, created_at`,
+		strings.TrimSpace(in.Name), prefix, hash, owner, tier, rate, createdBy,
+	).Scan(&row.ID, &row.Name, &row.KeyPrefix, &row.OwnerEmail, &row.Tier,
+		&row.RateLimitPerMin, &revoked, &createdByOut, &created)
+	if err != nil {
+		return "", row, err
+	}
+	row.CreatedBy = createdByOut
+	if created != nil {
+		row.CreatedAt = created.Format(time.RFC3339)
+	}
+	return key, row, nil
+}
+
+// ListAPIKeys returns all keys (active first, newest first).
+func (s *Store) ListAPIKeys(ctx context.Context) ([]APIKeyRow, error) {
+	rows, err := s.pool.Query(ctx, `
+SELECT id, name, key_prefix, owner_email, tier, rate_limit_per_min, revoked_at, created_by, created_at
+FROM api_key
+ORDER BY (revoked_at IS NULL) DESC, created_at DESC`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := []APIKeyRow{}
+	for rows.Next() {
+		var r APIKeyRow
+		var revoked, created *time.Time
+		if err := rows.Scan(&r.ID, &r.Name, &r.KeyPrefix, &r.OwnerEmail, &r.Tier,
+			&r.RateLimitPerMin, &revoked, &r.CreatedBy, &created); err != nil {
+			return nil, err
+		}
+		if revoked != nil {
+			v := revoked.Format(time.RFC3339)
+			r.RevokedAt = &v
+		}
+		if created != nil {
+			r.CreatedAt = created.Format(time.RFC3339)
+		}
+		out = append(out, r)
+	}
+	return out, rows.Err()
+}
+
+// RevokeAPIKey marks a key revoked. Revoking an already-revoked or missing key
+// returns ErrNotFound.
+func (s *Store) RevokeAPIKey(ctx context.Context, id string) error {
+	tag, err := s.pool.Exec(ctx,
+		"UPDATE api_key SET revoked_at = now() WHERE id = $1 AND revoked_at IS NULL", id)
+	if err != nil {
+		if isInvalidUUID(err) {
+			return ErrNotFound
+		}
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+// isInvalidUUID reports whether err is a Postgres invalid-UUID-text error,
+// which happens when a non-UUID id is supplied.
+func isInvalidUUID(err error) bool {
+	var pgErr *pgconn.PgError
+	if errors.As(err, &pgErr) {
+		return pgErr.Code == "22P02"
+	}
+	return false
+}