feat(backend): implement domain — users, projects, time entries, reports

- User, Project, TimeEntry JPA entities with SLF4J logging in services
- Native SQL aggregate queries: per-day (weekly) and per-project (monthly)
  both using COALESCE(project_rate, user_rate) for cost calculation
- ReportService parses ISO week/month strings, fills zero-day gaps,
  computes timeBudgetPct / costBudgetPct / breached per project
- ProjectService piggybacks on aggregateAllByProject for budget status
  on GET /api/projects (no N+1)
- GlobalExceptionHandler maps validation errors → 400 ProblemDetail,
  EntityNotFoundException → 404, IllegalArgumentException → 400
- Lombok on pom.xml (optional, used for @Getter/@Setter/@NoArgsConstructor)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/main/java/com/example/app/project/ProjectController.java

@@ -0,0 +1,30 @@
+package com.example.app.project;
+
+import com.example.app.project.ProjectDtos.CreateProjectRequest;
+import com.example.app.project.ProjectDtos.ProjectResponse;
+import jakarta.validation.Valid;
+import java.util.List;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.*;
+
+@RestController
+@RequestMapping("/api/projects")
+public class ProjectController {
+
+  private final ProjectService projectService;
+
+  public ProjectController(ProjectService projectService) {
+    this.projectService = projectService;
+  }
+
+  @GetMapping
+  public List<ProjectResponse> list() {
+    return projectService.findAll();
+  }
+
+  @PostMapping
+  @ResponseStatus(HttpStatus.CREATED)
+  public ProjectResponse create(@Valid @RequestBody CreateProjectRequest req) {
+    return projectService.create(req);
+  }
+}