Add platform powder catalog, catalog-first lookup, and label scanner

- Platform PowderCatalogItem table (IPlainRepository, no tenant filter) with
  full spec fields: cure temp/time, finish, color families, clear coat flag,
  coverage sq ft/lb, transfer efficiency, IsUserContributed
- Two EF migrations: AddPowderCatalogItem + AddPowderCatalogSpecFields
- PowderCatalogController (SuperAdminOnly): import from Prismatic JSON scrape,
  Lookup AJAX endpoint (catalog-first, ranked by SKU exact match), stats view
  with Tenant Contributed card
- Unified smart Lookup button on inventory Create/Edit: catalog hit fills all
  fields via catalogSnapshot pattern; AI augments cure/finish data from product
  URL if subscription enabled; catalog miss falls through to AI lookup
- In-browser label scanner (_LabelScanModal): getUserMedia live camera feed,
  jsQR auto-detects QR codes in rAF loop; "Scan Label Text" fallback sends
  captured frame to Claude vision via /Inventory/ScanLabel
- ScanLabel endpoint handles both QR URL path (LookupByUrlAsync) and vision
  path (ScanLabelAsync); auto-inserts unrecognized products as
  IsUserContributed=true; returns wasInCatalog/addedToCatalog flags

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Application/Interfaces/IInventoryAiLookupService.cs

@@ -40,4 +40,16 @@ public interface IInventoryAiLookupService
         string? colorName,
         string? colorCode,
         string? partNumber);
+
+    /// <summary>
+    /// Fetch cure specs, color families, finish, and clear-coat data from a known product URL.
+    /// Skips the Serper search step; used after a catalog hit to augment catalog fields.
+    /// </summary>
+    Task<InventoryAiLookupResult> LookupByUrlAsync(string url, string? colorName);
+
+    /// <summary>
+    /// Read a powder label photo and extract manufacturer, color name, SKU, and cure specs
+    /// using Claude vision. Used by the in-browser label scanner.
+    /// </summary>
+    Task<InventoryAiLookupResult> ScanLabelAsync(string base64Image, string mediaType);
 }