Initial commit

src/PowderCoating.Infrastructure/Services/AiUsageLogger.cs

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+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using PowderCoating.Application.Interfaces;
+using PowderCoating.Core.Entities;
+using PowderCoating.Infrastructure.Data;
+
+namespace PowderCoating.Infrastructure.Services;
+
+/// <summary>
+/// Writes one AiUsageLog row per Anthropic API call using a fresh DI scope so the insert
+/// is fully isolated from the caller's Unit-of-Work transaction. Registered as Singleton
+/// because IServiceScopeFactory is singleton-safe and we want zero allocation overhead on
+/// every AI request.
+/// </summary>
+public class AiUsageLogger : IAiUsageLogger
+{
+    private readonly IServiceScopeFactory _scopeFactory;
+    private readonly ILogger<AiUsageLogger> _logger;
+
+    public AiUsageLogger(IServiceScopeFactory scopeFactory, ILogger<AiUsageLogger> logger)
+    {
+        _scopeFactory = scopeFactory;
+        _logger = logger;
+    }
+
+    /// <inheritdoc/>
+    public async Task LogAsync(int companyId, string userId, string feature, bool success = true, int inputLength = 0)
+    {
+        try
+        {
+            using var scope = _scopeFactory.CreateScope();
+            var context = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+            context.AiUsageLogs.Add(new AiUsageLog
+            {
+                CompanyId  = companyId,
+                UserId     = userId,
+                Feature    = feature,
+                Success    = success,
+                InputLength = inputLength,
+                CalledAt   = DateTime.UtcNow
+            });
+            await context.SaveChangesAsync();
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "AI usage log write failed for company {CompanyId} feature {Feature} — non-fatal", companyId, feature);
+        }
+    }
+}