feat: enhance security with IP banning, ownership checks, and SSRF protection

Add comprehensive security improvements across the application:

- **IP-based login protection**: Implement IP ban system tracking login failures, auto-banning after threshold exceeded
- **Ownership verification**: Add userID parameter to Delete/Update operations for posts and comments to prevent unauthorized modifications
- **SSRF protection**: Add URL and resolved host validation for image URLs in chat and OpenAI client
- **SQL injection prevention**: Add EscapeLikeWildcard utility to escape special characters in LIKE queries
- **HTTP security**: Configure server timeouts and add security headers middleware
- **Rate limiting**: Refactor to support configurable duration and per-endpoint rate limits for auth routes
- **Error handling**: Standardize error responses using HandleError and proper error types

internal/handler/notification_handler.go

@@ -56,7 +56,7 @@ func (h *NotificationHandler) MarkAsRead(c *gin.Context) {
 
 	err := h.notificationService.MarkAsReadWithUserID(c.Request.Context(), id, userID)
 	if err != nil {
-		response.InternalServerError(c, "failed to mark as read")
+		response.HandleError(c, err, "failed to mark as read")
 		return
 	}
 
@@ -109,7 +109,7 @@ func (h *NotificationHandler) DeleteNotification(c *gin.Context) {
 
 	err := h.notificationService.DeleteNotification(c.Request.Context(), id, userID)
 	if err != nil {
-		response.InternalServerError(c, "failed to delete notification")
+		response.HandleError(c, err, "failed to delete notification")
 		return
 	}