Add platform powder catalog management UI with full CRUD and AI lookup

- PowderCatalogController: Create, Edit, ToggleDiscontinued actions; searchable/filterable/sortable Index with pagination; AiLookup and AiAugmentFromUrl endpoints backed by IInventoryAiLookupService
- New views: Create, Edit, _Form partial (with AI-assisted field population), overhauled Index grid with completeness quality badges and responsive mobile cards
- New ViewModels: PowderCatalogIndexViewModel, PowderCatalogFormViewModel, PowderCatalogListItemViewModel
- AI lookup improvements: SpecificGravity field added to InventoryAiLookupResult; ApplyPowderFallbacks derives CoverageSqFtPerLb from specific gravity when docs omit it; DefaultTransferEfficiency (65%) applied everywhere transfer efficiency is null
- powder-catalog-ai-lookup.js: client-side AI lookup and URL augment wiring for the catalog form

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

src/PowderCoating.Application/Interfaces/IInventoryAiLookupService.cs

@@ -20,6 +20,7 @@ public class InventoryAiLookupResult
     public bool? RequiresClearCoat { get; set; }
 
     // Application properties
+    public decimal? SpecificGravity { get; set; }   // used to derive theoretical coverage when docs omit coverage
     public decimal? CoverageSqFtPerLb { get; set; }  // typical ~80-120 sq ft/lb
     public decimal? TransferEfficiency { get; set; }  // typical 50-75%
     public decimal? UnitCostPerLb { get; set; }       // price per lb/unit if found in search results