Lazily enrich catalog specs from TDS on first use

Specific gravity, coverage, and ~55% of cure specs aren't in the Columbia feed.
Rather than read 2,400 TDS PDFs up front, enrich a catalog item the first time
it's actually used:

- FetchTdsCureSpecsAsync now also extracts specific gravity from the TDS.
- New EnsureCatalogTdsSpecsAsync fills a catalog item's specific gravity (and
  any missing cure temp/time) from its TDS, then derives theoretical coverage
  (192.3 / (SG x mils)). No-op once specific gravity is known or when there's no
  TDS; persists to the catalog so the work is done once and benefits everyone.
- Hooked into the catalog->inventory paths (CreateIncomingFromCatalog, the
  custom-powder receive enrichment, and ReceivePowderFromCatalog) so a powder's
  full specs land on both the catalog and the new inventory record. DashboardController
  gains the AI lookup service for this.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Infrastructure/Services/InventoryAiLookupService.cs

@@ -6,6 +6,7 @@ using Anthropic.SDK.Messaging;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Logging;
 using PowderCoating.Application.Interfaces;
+using PowderCoating.Core.Entities;
 using PowderCoating.Core.Interfaces;
 
 namespace PowderCoating.Infrastructure.Services;
@@ -541,18 +542,20 @@ Rules:
 
             // Targeted prompt: we only need cure specs from this document
             const string curePrompt = @"You are reading a Technical Data Sheet (TDS) for a powder coating product.
-Extract ONLY the cure schedule. Respond with a valid JSON object — no markdown, no explanation:
+Extract the cure schedule and the specific gravity. Respond with a valid JSON object — no markdown, no explanation:
 
 {
   ""cureTemperatureF"": number or null,
   ""cureTimeMinutes"": number or null,
-  ""reasoning"": ""one sentence: what cure schedule you found""
+  ""specificGravity"": number or null,
+  ""reasoning"": ""one sentence: what cure schedule and specific gravity you found""
 }
 
 Rules:
 - cureTemperatureF: the recommended cure temperature in °F. Convert from °C if needed (multiply by 1.8 + 32). If a range is given use the midpoint. Most powders cure 325–400 °F.
 - cureTimeMinutes: the hold time at cure temperature in minutes (NOT total oven time). Typically 10–20 min.
-- If neither value can be found in the document, return null for both.";
+- specificGravity: the specific gravity / density value from the TDS (often labeled ""Specific Gravity"" or ""Density""). Typically 1.2–1.8. Null if not stated.
+- Return null for any value not found in the document.";
 
             var sb = new StringBuilder();
             sb.AppendLine("Technical Data Sheet content:");
@@ -603,11 +606,12 @@ Rules:
                 Success          = true,
                 CureTemperatureF = GetDecimal(parsed, "cureTemperatureF"),
                 CureTimeMinutes  = GetInt(parsed,     "cureTimeMinutes"),
+                SpecificGravity  = GetDecimal(parsed, "specificGravity"),
                 Reasoning        = GetString(parsed,  "reasoning"),
             };
 
-            _logger.LogInformation("TDS cure lookup for {Url}: temp={Temp}°F, time={Time}min ({Reasoning})",
-                tdsUrl, result.CureTemperatureF, result.CureTimeMinutes, result.Reasoning);
+            _logger.LogInformation("TDS spec lookup for {Url}: temp={Temp}°F, time={Time}min, sg={Sg} ({Reasoning})",
+                tdsUrl, result.CureTemperatureF, result.CureTimeMinutes, result.SpecificGravity, result.Reasoning);
             return result;
         }
         catch (Exception ex)
@@ -617,6 +621,58 @@ Rules:
         }
     }
 
+    /// <inheritdoc />
+    public async Task<bool> EnsureCatalogTdsSpecsAsync(PowderCatalogItem catalog)
+    {
+        // Already enriched, or nothing to read from. Specific gravity is the trigger: it's never in
+        // the API feed, so its absence means this item hasn't been TDS-enriched yet.
+        if (catalog == null || catalog.SpecificGravity.HasValue || string.IsNullOrWhiteSpace(catalog.TdsUrl))
+            return false;
+
+        var tds = await FetchTdsCureSpecsAsync(catalog.TdsUrl, catalog.ColorName);
+        if (!tds.Success)
+            return false;
+
+        var changed = false;
+
+        if (tds.SpecificGravity is > 0)
+        {
+            catalog.SpecificGravity = tds.SpecificGravity;
+            changed = true;
+        }
+        if (!catalog.CureTemperatureF.HasValue && tds.CureTemperatureF.HasValue)
+        {
+            catalog.CureTemperatureF = tds.CureTemperatureF;
+            changed = true;
+        }
+        if (!catalog.CureTimeMinutes.HasValue && tds.CureTimeMinutes.HasValue)
+        {
+            catalog.CureTimeMinutes = tds.CureTimeMinutes;
+            changed = true;
+        }
+        // Derive theoretical coverage once specific gravity is known.
+        if (!catalog.CoverageSqFtPerLb.HasValue && catalog.SpecificGravity is > 0)
+        {
+            catalog.CoverageSqFtPerLb = Math.Round(
+                TheoreticalCoverageConstant / (catalog.SpecificGravity.Value * DefaultCoverageThicknessMils),
+                2, MidpointRounding.AwayFromZero);
+            changed = true;
+        }
+
+        if (changed)
+        {
+            catalog.UpdatedAt = DateTime.UtcNow;
+            await _unitOfWork.PowderCatalog.UpdateAsync(catalog);
+            await _unitOfWork.CompleteAsync();
+            _logger.LogInformation(
+                "Lazily enriched catalog item {Vendor} {Sku} from TDS: sg={Sg}, cure={Temp}F/{Time}min, coverage={Cov}",
+                catalog.VendorName, catalog.Sku, catalog.SpecificGravity, catalog.CureTemperatureF,
+                catalog.CureTimeMinutes, catalog.CoverageSqFtPerLb);
+        }
+
+        return changed;
+    }
+
     // ── Manufacturer URL pattern: build direct product page URL ───────────────
 
     /// <summary>