Document AI Catalog Price Check in knowledge base and help article

- HelpKnowledgeBase: full AI price check section (verdicts, confidence,
  category paths, run limit, how to use, common questions)
- Inventory help article: new 'AI Catalog Price Check' section with
  verdicts, step-by-step instructions, caveats, and on-page nav link

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

src/PowderCoating.Web/Helpers/HelpKnowledgeBase.cs

@@ -959,6 +959,42 @@ public static class HelpKnowledgeBase
 
         ---
 
+        ## AI CATALOG PRICE CHECK
+
+        **Where:** [Catalog Items](/CatalogItems) → "AI Price Check" button (top-right of the catalog list)
+
+        **What it does:** Reviews every active, priced catalog item against your shop's actual operating costs. For each item the AI estimates a realistic surface area and processing time, calculates a cost floor (labor + equipment + materials), then compares that to the item's current price and returns a verdict. Results are saved so you can review them any time without re-running the analysis.
+
+        **Verdicts:**
+        - **Below Cost** — price is at or below the cost floor; the shop loses money on this item
+        - **Thin Margin** — price is above cost but below the shop's target margin
+        - **High** — price appears significantly above typical market rates
+        - **OK** — price is within a reasonable range
+
+        **Confidence levels:** Each result shows a confidence level (High / Medium / Low) based on how specific the item name is. Vague items like "Custom Part" or "Special Job" will be flagged as Low confidence — treat those results with extra skepticism.
+
+        **Category paths:** The AI uses the full category path (e.g. "Cerakote > Firearms") to determine the coating process. Cerakote and other specialty coatings have very different cost profiles than standard powder coat — make sure items are in the correct category for the most accurate results.
+
+        **Run limit:** Analysis can be run once per quarter (every 90 days). The button shows the next available date when a recent run exists. This limit applies per company.
+
+        **Before running:** Make sure your operating costs (labor rate, oven cost, powder cost, etc.) are up to date in [Company Settings](/CompanySettings). Stale costs will produce inaccurate verdicts.
+
+        **How to use the results:**
+        1. Go to Catalog Items → click "AI Price Check"
+        2. Click "Analyze Catalog with AI" — a progress overlay shows estimated completion time (allow 7–10 minutes for large catalogs)
+        3. Review the results sorted by severity (Below Cost first, then Thin Margin, High, OK)
+        4. For flagged items, click "Edit Price" to update the price directly from the results page
+        5. Items marked Low confidence should be verified manually — the AI had limited information to work with
+
+        **Common questions:**
+        - "How accurate is the AI analysis?" → Results are estimates based on industry knowledge and your operating costs. Always apply your own judgment before changing prices.
+        - "Why is an item showing $0.00 cost floor?" → The item likely had an error during analysis. Re-run the check or verify the item has a valid name and category.
+        - "Can I run it more often?" → The quarterly limit is enforced to manage costs. Contact your administrator if you need an exception.
+        - "Items in my Cerakote category are priced wrong" → Make sure those items are in a category whose full path includes 'Cerakote' (e.g. "Cerakote > Firearms"). The AI uses the category path to determine the coating type.
+        - "The progress bar finished but the page didn't load" → The analysis is still running server-side. Wait for the page to redirect automatically — do not close the tab.
+
+        ---
+
         ## USER PROFILE
 
         **Where:** [My Profile](/Profile) — via the user menu (top-right)