fix: remove incorrect cents-to-dollars conversion in notification email amounts

[devin-ai-integration]

Summary

Order confirmation emails displayed wrong amounts (e.g., $149.99 order showed as $1.50) because NotificationRenderer.FormatCurrency() incorrectly divided by 100:

// NotificationRenderer.cs
  private static string FormatCurrency(decimal amount)
  {
-     // The OrderPlacedEvent.TotalAmount is transmitted in cents ...
-     var dollars = amount / 100m;
-     return dollars.ToString("C2");
+     return amount.ToString("C2");
  }

The comment claimed OrderPlacedEvent.TotalAmount was in cents, but the shared contract (Shared.Contracts.Events.OrderPlacedEvent) defines it as decimal TotalAmount — already in dollars. The division turned 149.99 into 1.4999, which rounded to $1.50.

Also fixes Notification.API.csproj project reference paths to Shared libraries (../../Shared -> ../../../Shared) to match the actual directory layout under src/.

Root Cause Analysis

The bug was introduced during microservice decomposition. The FormatCurrency method was written with an incorrect assumption (documented in a misleading comment) that the TotalAmount field was transmitted in cents for "floating-point precision" reasons. In reality, the OrderPlacedEvent contract uses decimal (which has no floating-point precision issues) and transmits the dollar amount directly.

Before

After

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/bf6d422091a1474691a1c26910179d93
Requested by: @alagarrajanm

[devin-ai-integration]

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