feat(markers): implement marker entity & service

src/main/java/com/ddf/vodsystem/controllers/dto/MarkerCreateRequest.java

@@ -0,0 +1,7 @@
+package com.ddf.vodsystem.controllers.dto;
+
+import jakarta.validation.constraints.NotBlank;
+
+public record MarkerCreateRequest(
+        @NotBlank String message
+) {}

src/main/java/com/ddf/vodsystem/controllers/dto/MarkerResponse.java

@@ -0,0 +1,11 @@
+package com.ddf.vodsystem.controllers.dto;
+
+import java.time.Instant;
+
+public record MarkerResponse(
+        Long id,
+        Long userId,
+        Long streamId,
+        String message,
+        Instant timestamp
+) {}