feat: implement SSE real-time streaming for simulations

backend/src/main/java/com/algorithmrace/visualizer/controller/StreamController.java

@@ -0,0 +1,43 @@
+package com.algorithmrace.visualizer.controller;
+
+import com.algorithmrace.visualizer.dto.PathfindingSimulationRequest;
+import com.algorithmrace.visualizer.dto.SearchingSimulationRequest;
+import com.algorithmrace.visualizer.dto.SortingSimulationRequest;
+import com.algorithmrace.visualizer.service.StreamingService;
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.ModelAttribute;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+@RestController
+@RequestMapping("/api/simulations/stream")
+@Tag(name = "Stream", description = "Endpoints for streaming algorithm simulations via SSE")
+public class StreamController {
+
+  private final StreamingService streamingService;
+
+  public StreamController(StreamingService streamingService) {
+    this.streamingService = streamingService;
+  }
+
+  @Operation(summary = "Stream sorting simulation")
+  @GetMapping("/sorting")
+  public SseEmitter streamSorting(@ModelAttribute SortingSimulationRequest request) {
+    return streamingService.streamSorting(request);
+  }
+
+  @Operation(summary = "Stream searching simulation")
+  @GetMapping("/searching")
+  public SseEmitter streamSearching(@ModelAttribute SearchingSimulationRequest request) {
+    return streamingService.streamSearching(request);
+  }
+
+  @Operation(summary = "Stream pathfinding simulation")
+  @GetMapping("/pathfinding")
+  public SseEmitter streamPathfinding(@ModelAttribute PathfindingSimulationRequest request) {
+    return streamingService.streamPathfinding(request);
+  }
+}

backend/src/main/java/com/algorithmrace/visualizer/dto/LaneFrameEvent.java

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+package com.algorithmrace.visualizer.dto;
+
+public record LaneFrameEvent(String laneName, SimulationFrame frame) {}