Fix label scanner: full field mapping, vision follow-up lookup, SDS/TDS extraction

- LookupByUrlAsync now maps all identity + spec fields from Claude response
  (manufacturer, SKU, colorName, description, sdsUrl, tdsUrl, unitCostPerLb, etc.)
  Previously only augmenting fields were mapped; Columbia QR path left 80% blank
- Vision scan follow-up: after ScanLabelAsync reads label text, automatically run
  LookupAsync using the extracted manufacturer + color/SKU to fill SDS/TDS URLs,
  product page, image, description, and any specs not printed on the bag;
  label values (cure schedule, SKU) remain authoritative and are never overwritten
- SDS/TDS URL extraction: added ExtractDocumentLinks() that scans anchor tags in
  raw HTML before tag-stripping, injects found URLs as [Structured Data] lines so
  Claude can read and echo them back in the JSON response; previously all hrefs
  were lost with the HTML stripping
- Added SdsUrl/TdsUrl to InventoryAiLookupResult, Claude system prompt JSON schema,
  LookupAsync mapping, and ScanLabel response (catalog match ?? aiResult fallback)
- SDS/TDS now also stored on auto-contributed catalog entries
- jsQR inversionAttempts: 'dontInvert' → 'attemptBoth' for better QR detection
  under varying label contrast and lighting conditions

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

src/PowderCoating.Web/wwwroot/js/inventory-label-scan.js

@@ -104,7 +104,7 @@
                 ctx.drawImage(videoEl, 0, 0);
                 const imageData = ctx.getImageData(0, 0, canvasEl.width, canvasEl.height);
                 const code = window.jsQR(imageData.data, imageData.width, imageData.height, {
-                    inversionAttempts: 'dontInvert'
+                    inversionAttempts: 'attemptBoth'
                 });
 
                 if (code && code.data) {