Merge remote-tracking branch 'origin/dev' into fix-pr-11

# Conflicts:
#	backend/Program.cs

backend/API/Controllers/CostAnalysisController.cs

@@ -0,0 +1,108 @@
+using Extrudex.API.DTOs.PrintJobs;
+using Extrudex.Domain.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace Extrudex.API.Controllers;
+
+/// <summary>
+/// Controller for cost analysis endpoints. Provides spool-level
+/// cost breakdowns and aggregated COGS reporting.
+/// </summary>
+[ApiController]
+[Route("api/cost-analysis")]
+public class CostAnalysisController : ControllerBase
+{
+    private readonly ICostPerPrintService _costService;
+    private readonly ILogger<CostAnalysisController> _logger;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="CostAnalysisController"/> class.
+    /// </summary>
+    /// <param name="costService">The cost-per-print calculation service.</param>
+    /// <param name="logger">The logger for diagnostic output.</param>
+    public CostAnalysisController(
+        ICostPerPrintService costService,
+        ILogger<CostAnalysisController> logger)
+    {
+        _costService = costService;
+        _logger = logger;
+    }
+
+    // ── POST /api/cost-analysis/spool ────────────────────────────
+
+    /// <summary>
+    /// Calculates cost breakdowns for all print jobs associated with a specific spool.
+    /// Returns per-job costs plus an aggregated total. Jobs with missing cost data
+    /// include warnings and null cost fields — the endpoint never throws for missing data.
+    /// </summary>
+    /// <param name="request">The request containing the spool identifier.</param>
+    /// <returns>A spool-level cost summary with per-job breakdowns.</returns>
+    /// <response code="200">Returns the spool cost breakdown with per-job details.</response>
+    /// <response code="404">If the spool has no print jobs.</response>
+    [HttpPost("spool")]
+    [ProducesResponseType(typeof(SpoolCostResponse), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<SpoolCostResponse>> CalculateSpoolCost([FromBody] SpoolCostRequest request)
+    {
+        _logger.LogDebug("Calculating cost breakdown for spool {SpoolId}", request.SpoolId);
+
+        var results = await _costService.CalculateBySpoolAsync(request.SpoolId);
+
+        if (results.Count == 0)
+        {
+            return NotFound(new { error = $"No print jobs found for spool with ID '{request.SpoolId}'." });
+        }
+
+        // Build the spool-level summary
+        var firstResult = results[0];
+        var jobResponses = results.Select(MapCostToResponse).ToList();
+
+        // Aggregate total cost and grams — only include jobs that have a valid cost
+        var calculableJobs = results.Where(r => r.CostPerPrint.HasValue).ToList();
+        var totalCost = calculableJobs.Count == results.Count
+            ? Math.Round(calculableJobs.Sum(r => r.CostPerPrint!.Value), 4)
+            : (decimal?)null;
+
+        var aggregateWarnings = new List<string>();
+        if (calculableJobs.Count < results.Count)
+        {
+            aggregateWarnings.Add(
+                $"{results.Count - calculableJobs.Count} of {results.Count} print jobs have missing cost data. " +
+                "Total cost reflects only jobs with complete data.");
+        }
+
+        var response = new SpoolCostResponse
+        {
+            SpoolId = request.SpoolId,
+            SpoolSerial = firstResult.SpoolSerial,
+            PurchasePrice = firstResult.PurchasePrice,
+            WeightTotalGrams = firstResult.WeightTotalGrams,
+            CostPerGram = firstResult.CostPerGram,
+            TotalGramsConsumed = results.Sum(r => r.GramsDerived),
+            TotalCost = totalCost,
+            JobCount = results.Count,
+            Jobs = jobResponses,
+            Warnings = aggregateWarnings
+        };
+
+        return Ok(response);
+    }
+
+    /// <summary>
+    /// Maps a domain CostPerPrintResult to an API CostPerPrintResponse DTO.
+    /// </summary>
+    private static CostPerPrintResponse MapCostToResponse(CostPerPrintResult r) => new()
+    {
+        PrintJobId = r.PrintJobId,
+        PrintName = r.PrintName,
+        SpoolId = r.SpoolId,
+        SpoolSerial = r.SpoolSerial,
+        MmExtruded = r.MmExtruded,
+        GramsDerived = r.GramsDerived,
+        PurchasePrice = r.PurchasePrice,
+        WeightTotalGrams = r.WeightTotalGrams,
+        CostPerGram = r.CostPerGram,
+        CostPerPrint = r.CostPerPrint,
+        Warnings = r.Warnings
+    };
+}