Update help docs and AI knowledge base for new features

GettingStarted: add 'Using on Mobile — Add to Home Screen' section covering
iOS Safari install flow, Android Chrome install, and PWA benefits (full-screen,
persistent camera permission). Includes Safari-required warning for iOS.

Inventory: add 'Catalog Lookup & Label Scanner' section covering smart catalog
search (filters out existing inventory, vendor-scoped with fallback), AI Lookup
fallback, camera label scanner (catalog-first then AI), and the add-stock prompt
when a scanned product is already in inventory.

HelpKnowledgeBase: sync both of the above for the AI Help Assistant, plus add
catalog lookup / label scanner detail to the INVENTORY section.

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

src/PowderCoating.Web/Helpers/HelpKnowledgeBase.cs

@@ -445,6 +445,14 @@ public static class HelpKnowledgeBase
         - Every scan log is recorded as a JobUsage or Adjustment InventoryTransaction and immediately reduces QuantityOnHand; visible in Inventory Activity ledger
         - First-time scan on a new device requires login; browser caches the session after that
 
+        **Catalog Lookup & Label Scanner (when adding/editing inventory items):**
+        - When creating or editing an inventory item, click the **Lookup** button next to the SKU/Part Number field to search a built-in platform catalog of thousands of Prismatic Powders and other manufacturer SKUs. Select a match to auto-fill name, manufacturer, color code, finish, coverage rate, SDS/TDS links, and cure specs.
+        - The catalog only shows products not already in the company's inventory (prevents duplicates). When editing, the item's own catalog entry is always shown.
+        - If no catalog match is found, the lookup falls back to **AI Lookup** — Claude searches the web for product specs and fills in what it finds.
+        - If a vendor is selected first, the search is scoped to that vendor; if nothing matches it automatically widens to all vendors.
+        - Click the **camera icon** (next to the Lookup button) to open the **Label Scanner** — point the phone camera at a QR code on a powder bag to identify the product automatically. It checks the platform catalog first; if not found, AI analyzes the label image.
+        - If the scanned product **already exists** in the company's inventory, a modal appears offering to **Add Stock** to the existing item instead — enter quantity received and optional updated cost. No duplicate item is created.
+
         **Powder Insights:** [/PowderInsights](/PowderInsights) — AI-powered analysis of powder usage trends, efficiency, and cost optimization. Requires at least 10 jobs with powder data; predictive features unlock at 150 jobs.
 
         ---
@@ -1148,6 +1156,32 @@ public static class HelpKnowledgeBase
 
         ---
 
+        ## MOBILE APP / ADD TO HOME SCREEN
+
+        Powder Coating Logix works in any phone browser but can also be installed as a **home screen app** (Progressive Web App / PWA) for a better experience. Installation is especially important for shop floor workers who use the label scanner or log usage from their phone.
+
+        **Why install it:**
+        - Opens full-screen with no browser address bar — feels like a native app
+        - Camera permission is granted once and remembered permanently (instead of being asked every browser session)
+        - Faster to launch — one tap from the home screen
+
+        **iOS (iPhone / iPad) — must use Safari:**
+        iOS only supports home screen installation from Safari. Installing from Chrome or Firefox on iOS creates a regular browser bookmark that does NOT give the standalone or camera-permission benefits.
+        1. Open the app in **Safari** (not Chrome or Firefox)
+        2. Tap the **Share button** (box with arrow pointing up) at the bottom of Safari
+        3. Scroll down and tap **Add to Home Screen**
+        4. Confirm the name and tap **Add**
+        The app icon now appears on the home screen and launches in full-screen mode.
+
+        **Android — Chrome:**
+        1. Open the app in Chrome
+        2. Chrome may show an **Install App** banner automatically — tap it
+        3. If no banner: tap the **menu (⋮)** in the top-right → **Add to Home Screen** or **Install App**
+
+        **Dashboard install banner:** When a mobile user who has not yet installed the app opens the Dashboard, a banner at the top of the page shows device-specific installation instructions. The banner disappears automatically once the app is running as a standalone home screen app, and can also be dismissed manually — it will not reappear after dismissal.
+
+        ---
+
         ## BUG REPORTS
 
         **Where:** [Bug Report](/BugReport)