Add usage events tracking for detailed analytics

- Add UsageEvent entity for tracking translation usage
- Add migration for UsageEvents table
- Add usage breakdown DTOs and endpoints
- Add organization member usage tracking

Author: nickprotop

cloud/src/LrmCloud.Api/Controllers/UsageController.cs

@@ -52,4 +52,43 @@ public async Task<ActionResult<ApiResponse<OrganizationUsageDto>>> GetOrganizati
 
         return Success(stats);
     }
+
+    /// <summary>
+    /// Get user's usage breakdown by personal vs organization contributions.
+    /// </summary>
+    [HttpGet("breakdown")]
+    public async Task<ActionResult<ApiResponse<UserUsageBreakdownDto>>> GetUserBreakdown()
+    {
+        var userId = GetUserId();
+        var breakdown = await _usageService.GetUserUsageBreakdownAsync(userId);
+        return Success(breakdown);
+    }
+
+    /// <summary>
+    /// Get organization usage breakdown by member (admins/owners only).
+    /// </summary>
+    [HttpGet("organizations/{organizationId:int}/members")]
+    public async Task<ActionResult<ApiResponse<List<OrgMemberUsageDto>>>> GetOrgMemberUsage(int organizationId)
+    {
+        var userId = GetUserId();
+        var usage = await _usageService.GetOrgMemberUsageAsync(organizationId, userId);
+        return Success(usage);
+    }
+
+    /// <summary>
+    /// Get project usage breakdown by contributor.
+    /// </summary>
+    [HttpGet("projects/{projectId:int}")]
+    public async Task<ActionResult<ApiResponse<ProjectUsageDto>>> GetProjectUsage(int projectId)
+    {
+        var userId = GetUserId();
+        var usage = await _usageService.GetProjectUsageAsync(projectId, userId);
+
+        if (usage == null)
+        {
+            return NotFound("Project not found or you don't have access to it.");
+        }
+
+        return Success(usage);
+    }
 }

cloud/src/LrmCloud.Api/Data/AppDbContext.cs

@@ -41,6 +41,9 @@ public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
     // Translation Usage History
     public DbSet<TranslationUsageHistory> TranslationUsageHistory => Set<TranslationUsageHistory>();
 
+    // Usage Events (detailed per-translation tracking)
+    public DbSet<UsageEvent> UsageEvents => Set<UsageEvent>();
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);
@@ -298,6 +301,40 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
             // Match parent's soft-delete filter
             entity.HasQueryFilter(e => e.User!.DeletedAt == null);
         });
+
+        // =====================================================================
+        // Usage Events (detailed per-translation tracking)
+        // =====================================================================
+        modelBuilder.Entity<UsageEvent>(entity =>
+        {
+            entity.HasIndex(e => e.ActingUserId);
+            entity.HasIndex(e => e.BilledUserId);
+            entity.HasIndex(e => e.ProjectId);
+            entity.HasIndex(e => e.OrganizationId);
+            entity.HasIndex(e => e.CreatedAt);
+            entity.HasIndex(e => new { e.OrganizationId, e.CreatedAt });
+            entity.HasIndex(e => new { e.ProjectId, e.CreatedAt });
+
+            entity.HasOne(e => e.ActingUser)
+                .WithMany()
+                .HasForeignKey(e => e.ActingUserId)
+                .OnDelete(DeleteBehavior.Cascade);
+
+            entity.HasOne(e => e.BilledUser)
+                .WithMany()
+                .HasForeignKey(e => e.BilledUserId)
+                .OnDelete(DeleteBehavior.Cascade);
+
+            entity.HasOne(e => e.Project)
+                .WithMany()
+                .HasForeignKey(e => e.ProjectId)
+                .OnDelete(DeleteBehavior.SetNull);
+
+            entity.HasOne(e => e.Organization)
+                .WithMany()
+                .HasForeignKey(e => e.OrganizationId)
+                .OnDelete(DeleteBehavior.SetNull);
+        });
     }
 
     /// <summary>