Add /config trial VPN generation for users (1 day default)

Users get Remnawave subscription via /config or inline button; TRIAL_USER_DAYS and panel lookup by Telegram ID.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/remnawave/users.go

@@ -19,14 +19,48 @@ type CreateUserInput struct {
 }
 
 type PanelUser struct {
-	UUID       string
-	Username   string
-	ShortUUID  string
-	Status     string
-	ExpireAt   time.Time
+	UUID            string
+	Username        string
+	ShortUUID       string
+	Status          string
+	ExpireAt        time.Time
 	SubscriptionURL string
 }
 
+func (c *Client) GetUserByUsername(ctx context.Context, username string) (*PanelUser, error) {
+	path := fmt.Sprintf("/api/users/by-username/%s", username)
+	resp, body, err := c.get(ctx, path)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode == http.StatusNotFound {
+		return nil, nil
+	}
+	if resp.StatusCode != http.StatusOK {
+		return nil, apiError(resp.StatusCode, body)
+	}
+	return parsePanelUser(body), nil
+}
+
+func (c *Client) GetUserByTelegramID(ctx context.Context, telegramID int64) (*PanelUser, error) {
+	path := fmt.Sprintf("/api/users/by-telegram-id/%d", telegramID)
+	resp, body, err := c.get(ctx, path)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode == http.StatusNotFound {
+		return nil, nil
+	}
+	if resp.StatusCode != http.StatusOK {
+		return nil, apiError(resp.StatusCode, body)
+	}
+	u := parsePanelUser(body)
+	if u == nil || u.UUID == "" {
+		return nil, nil
+	}
+	return u, nil
+}
+
 func (c *Client) CreateUser(ctx context.Context, in CreateUserInput) (*PanelUser, error) {
 	payload := map[string]any{
 		"username": in.Username,
@@ -118,6 +152,8 @@ func parsePanelUser(body []byte) *PanelUser {
 		if json.Unmarshal(raw, &s) == nil {
 			if t, err := time.Parse(time.RFC3339Nano, s); err == nil {
 				u.ExpireAt = t
+			} else if t, err := time.Parse(time.RFC3339, s); err == nil {
+				u.ExpireAt = t
 			}
 		}
 	}