fix: correct currency formatting in notification emails

[devin-ai-integration]

Summary

Order confirmation notification emails display incorrect monetary amounts. A $149.99 order renders as $1.50 (or ¤1.50 on non-US locales).

Root cause: NotificationRenderer.FormatCurrency divides the amount by 100, assuming OrderPlacedEvent.TotalAmount is in cents. In reality, TotalAmount is a decimal already representing dollars — the shared contract (Shared.Contracts.Events.OrderPlacedEvent) and the HTTP DTO both transmit dollar values, not cent integers.

// Before — incorrect: treats dollars as cents
- var dollars = amount / 100m;
- return dollars.ToString("C2");
// After — amount is already in dollars; use en-US culture for $ symbol
+ return amount.ToString("C2", CultureInfo.GetCultureInfo("en-US"));

The explicit en-US culture also fixes a secondary issue where Linux environments without a US locale rendered the generic currency symbol ¤ instead of $.

Also fixed: All five service .csproj files had broken ProjectReference paths to Shared.Contracts and Shared.Infrastructure — they used ..\..\Shared\ (resolves to src/Services/Shared/) instead of the correct ..\..\..\Shared\ (resolves to src/Shared/), preventing builds.

Before / After:

Before	After

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/c3de1ff27f2d42e8b4fa96d629e36bc9
Requested by: @sumitshatwara

[devin-ai-integration]

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