Inline item editing on Job Details with live pricing and costing updates

- PatchItem: add case-insensitive JSON deserialization; add legacy fallback
  that computes a live breakdown from job items when PricingBreakdownJson is null
- PatchItem: return itemsSubtotal, subtotalBeforeDiscount, subtotalAfterDiscount,
  taxAmount in JSON response for immediate DOM updates
- GetCostingBreakdown: use job.FinalPrice as revenue (not invoice total) so
  costing figures reflect inline edits before an invoice exists
- Details.cshtml: add data-pb attributes to visible pricing rows; add
  job-final-price-display class to visible Total element
- Details.cshtml: wire afterSave callback to call costing.load() after each edit
- inline-item-edit.js: add afterSave hook in commit(); clean up debug logging
- Help docs: add Inline Price Editing sections to Jobs, Quotes, and Invoices
  help articles; add inline editing + job costing revenue notes to AI knowledge base

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

src/PowderCoating.Web/Helpers/HelpKnowledgeBase.cs

@@ -215,6 +215,8 @@ public static class HelpKnowledgeBase
 
         **Per-item cost breakdown:** On the Quote Details page, each line item shows a collapsible cost breakdown — click the row to expand it and see how material, labor, equipment, complexity, and markup were calculated for that specific item. This is useful for spotting which items are underpriced or where costs are concentrated.
 
+        **Inline item editing on quotes:** On the Quote Details page, any unit price, quantity, or item description can be edited in-place by clicking the value directly. Press Enter or click away to save; press Escape to cancel. The pricing summary (subtotal, discount, tax, and total) updates immediately without reloading the page.
+
         **Pricing Mode (Markup vs Margin):** In Company Settings → Operating Costs you can choose between two pricing modes:
         - *Markup on Materials* (default) — the General Markup % is applied as a markup on top of calculated costs: `price = cost × (1 + markup%)`. A 25% markup on a $100 cost = $125.
         - *Target Margin on Total Cost* — the markup % is treated as a target gross margin: `price = cost ÷ (1 − margin%)`. A 25% margin on a $100 cost = $133.33. The difference grows at higher percentages.
@@ -305,6 +307,10 @@ public static class HelpKnowledgeBase
 
         **Changing the customer on a job:** On the Job Details page, the Customer field is an always-visible dropdown. Select a different customer — a confirmation banner appears. Click **Save** to apply or **Cancel** to revert. Use this to correct a misassigned job or to move a walk-in job to a customer's proper record after they've been added to the system.
 
+        **Inline item price editing:** On the Job Details page, any unit price, quantity, or item description can be edited in-place without opening the full edit form. Click the value — it becomes an input field. Type the new value, then press Enter or click away to save (Escape cancels). The pricing summary card (Items Subtotal, Subtotal, Tax, and Total) and the Job Costing card both update immediately without a page reload.
+
+        **Job Costing revenue:** The Job Costing card uses the job's Final Price as the revenue figure — not the linked invoice total. This means inline price edits are reflected in the profit margin estimate immediately, even before an invoice exists.
+
         **Completing a job:** When a job is ready to mark complete, click the **Complete Job** button on the Job Details page. A modal appears asking you to confirm the completion date, actual hours spent, and final price. If the job used powder from inventory, you will be asked to enter the actual lbs used — the modal groups all coats by unique powder color (not per coat or per item) so you fill in one quantity per powder. The system deducts the entered amounts from inventory, crediting any quantities already logged via QR scan. Once confirmed, the job advances to Completed status, and you are prompted to create the invoice if one does not exist.
 
         **Creating an invoice from a job:** On the Job Details page, look for the Invoice section and click "Create Invoice." The system pre-fills all line items, pricing, discount, tax rate, payment terms, and due date from the job and customer automatically. Line item descriptions include the coat color(s) for each item (e.g., "Color1 / Color2" if multiple coats), helping customers distinguish repeated items on the invoice. Review the Totals panel on the right — if a discount was applied to the job it will show as a red "Discount Applied" line. Adjust anything you need, then save.
@@ -357,6 +363,8 @@ public static class HelpKnowledgeBase
 
         **Payment methods:** Cash, Check, Credit/Debit Card, Bank Transfer (ACH), Digital Payment, Store Credit
 
+        **Inline item editing on invoices:** On the Invoice Details page, unit prices, quantities, and item descriptions can be edited in-place while the invoice is in Draft status. Click the value — it becomes an input field. Press Enter or click away to save; press Escape to cancel. The invoice total updates immediately. Line items are locked once the invoice is Sent.
+
         **Sending an invoice:** Invoice Details → "Send" — emails PDF to customer.
 
         **Online Payments:** [/Invoices/OnlinePayments](/Invoices/OnlinePayments) — Lists invoices with a shareable payment link the customer can pay without logging in. Requires Stripe Connect to be set up first (see below).