feat: 实现 OIDC 服务端会话与请求刷新

使用 AES-256-GCM 保存认证中心令牌，并以随机 Cookie 哈希关联 PostgreSQL 会话。加入闲置与绝对期限、Refresh Token 轮换以及多实例刷新锁。

apps/api/internal/oidcsession/crypto.go

@@ -0,0 +1,82 @@
+package oidcsession
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+)
+
+type TokenBundle struct {
+	AccessToken  string `json:"accessToken"`
+	RefreshToken string `json:"refreshToken"`
+	IDToken      string `json:"idToken,omitempty"`
+}
+
+type Cipher struct {
+	aead cipher.AEAD
+}
+
+func NewCipher(key []byte) (*Cipher, error) {
+	if len(key) != 32 {
+		return nil, errors.New("OIDC session encryption key must be exactly 32 bytes")
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	aead, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+	return &Cipher{aead: aead}, nil
+}
+
+func (c *Cipher) EncryptBundle(bundle TokenBundle, sessionID, gatewayUserID string) ([]byte, error) {
+	return c.SealJSON(bundle, tokenAAD(sessionID, gatewayUserID))
+}
+
+func (c *Cipher) SealJSON(value any, aad []byte) ([]byte, error) {
+	plaintext, err := json.Marshal(value)
+	if err != nil {
+		return nil, err
+	}
+	nonce := make([]byte, c.aead.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, err
+	}
+	return c.aead.Seal(nonce, nonce, plaintext, aad), nil
+}
+
+func (c *Cipher) DecryptBundle(encrypted []byte, sessionID, gatewayUserID string) (TokenBundle, error) {
+	var bundle TokenBundle
+	if err := c.OpenJSON(encrypted, tokenAAD(sessionID, gatewayUserID), &bundle); err != nil {
+		return TokenBundle{}, err
+	}
+	if bundle.AccessToken == "" || bundle.RefreshToken == "" {
+		return TokenBundle{}, errors.New("OIDC session token bundle is invalid")
+	}
+	return bundle, nil
+}
+
+func (c *Cipher) OpenJSON(encrypted, aad []byte, output any) error {
+	if len(encrypted) <= c.aead.NonceSize() {
+		return errors.New("OIDC session ciphertext is invalid")
+	}
+	nonce, ciphertext := encrypted[:c.aead.NonceSize()], encrypted[c.aead.NonceSize():]
+	plaintext, err := c.aead.Open(nil, nonce, ciphertext, aad)
+	if err != nil {
+		return errors.New("OIDC session ciphertext authentication failed")
+	}
+	if err := json.Unmarshal(plaintext, output); err != nil {
+		return errors.New("OIDC session ciphertext payload is invalid")
+	}
+	return nil
+}
+
+func tokenAAD(sessionID, gatewayUserID string) []byte {
+	return []byte(fmt.Sprintf("easyai-gateway/oidc-session/v1\x00%s\x00%s", sessionID, gatewayUserID))
+}