fix: P2 security and correctness issues

P2-10: Change ActivateEmail from GET to POST - token now passed in
request body instead of URL query parameter for better security

P2-11: Change ValidateResetToken from GET to POST - token now passed
in request body instead of URL query parameter to prevent log leakage

P2-12: Note - /uploads static exposure remains (requires architectural
decision about file serving)

P2-13: cursor.Encode() now checks and returns empty string on JSON
marshaling error instead of silently ignoring

P2-14: initDefaultData and ensurePermissions now properly check and
propagate errors from RolePermission creation, and createDefaultPermissions
aggregates errors instead of silently continuing

P2-15: NewJWT now returns (nil, error) on initialization failure
instead of a partially initialized object. All callers updated to handle
the error return.

Backend routes updated:
- POST /auth/activate-email (was GET /activate)
- POST /auth/password/validate (was GET /reset-password)

Frontend updated to match new API endpoints.

internal/api/handler/password_reset_handler.go

@@ -27,6 +27,11 @@ func NewPasswordResetHandlerWithSMS(passwordResetService *service.PasswordResetS
 	}
 }
 
+// ValidateResetTokenRequest 验证重置令牌请求
+type ValidateResetTokenRequest struct {
+	Token string `json:"token" binding:"required"`
+}
+
 // ForgotPassword 忘记密码
 // @Summary 忘记密码
 // @Description 请求密码重置邮件
@@ -59,19 +64,20 @@ func (h *PasswordResetHandler) ForgotPassword(c *gin.Context) {
 // @Summary 验证密码重置 Token
 // @Description 验证密码重置链接中的 Token 是否有效
 // @Tags 密码重置
+// @Accept json
 // @Produce json
-// @Param token query string true "重置 Token"
+// @Param request body ValidateResetTokenRequest true "重置 Token"
 // @Success 200 {object} Response{data=ValidateTokenResponse} "Token验证结果"
 // @Failure 400 {object} Response "请求参数错误"
-// @Router /api/v1/auth/password/validate [get]
+// @Router /api/v1/auth/password/validate [post]
 func (h *PasswordResetHandler) ValidateResetToken(c *gin.Context) {
-	token := c.Query("token")
-	if token == "" {
+	var req ValidateResetTokenRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "token is required"})
 		return
 	}
 
-	valid, err := h.passwordResetService.ValidateResetToken(c.Request.Context(), token)
+	valid, err := h.passwordResetService.ValidateResetToken(c.Request.Context(), req.Token)
 	if err != nil {
 		handleError(c, err)
 		return