fix: unify handler response format in multiple handlers

- captcha_handler.go: Fix GenerateCaptcha/VerifyCaptcha to use {code, message, data}
- password_reset_handler.go: Fix all error responses to use {code, message}
- settings_handler.go: Add missing "code" and "message" fields
- sms_handler.go: Fix error responses to use {code, message}
- sso_handler.go: Fix all error responses to use {code, message, data}
- stats_handler.go: Add missing "message" field in success responses
- theme_handler.go: Fix error responses to use {code, message}
- totp_handler.go: Fix all responses to use {code, message, data}

Standardize all JSON responses to {code: 0, message: "success", data: ...} for success
and {code: XXX, message: "..."} for errors.

internal/api/handler/theme_handler.go

@@ -23,7 +23,7 @@ func NewThemeHandler(themeService *service.ThemeService) *ThemeHandler {
 func (h *ThemeHandler) CreateTheme(c *gin.Context) {
 	var req service.CreateThemeRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
 		return
 	}
 
@@ -44,13 +44,13 @@ func (h *ThemeHandler) CreateTheme(c *gin.Context) {
 func (h *ThemeHandler) UpdateTheme(c *gin.Context) {
 	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid theme id"})
+		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid theme id"})
 		return
 	}
 
 	var req service.UpdateThemeRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
 		return
 	}
 
@@ -71,7 +71,7 @@ func (h *ThemeHandler) UpdateTheme(c *gin.Context) {
 func (h *ThemeHandler) DeleteTheme(c *gin.Context) {
 	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid theme id"})
+		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid theme id"})
 		return
 	}
 
@@ -90,7 +90,7 @@ func (h *ThemeHandler) DeleteTheme(c *gin.Context) {
 func (h *ThemeHandler) GetTheme(c *gin.Context) {
 	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid theme id"})
+		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid theme id"})
 		return
 	}
 
@@ -156,7 +156,7 @@ func (h *ThemeHandler) GetDefaultTheme(c *gin.Context) {
 func (h *ThemeHandler) SetDefaultTheme(c *gin.Context) {
 	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid theme id"})
+		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid theme id"})
 		return
 	}