Upgrade to structured logging #1769

Update this repository to use the structured logging support introduced in Shared PR #1339.

Replace interpolated or preformatted log messages with message templates and named properties. For example:

Logger.LogInformation(
    "Processed transaction {transactionId} for {amount} {currency}",
    transactionId,
    amount,
    currency);

Acceptance criteria

• Relevant logging calls use message templates with named properties.
• Exceptions are passed through the exception-aware logging overloads.
• Tenant and correlation context is available in log events where applicable.
• Logging configuration and consumers support the structured event properties.
• Existing logging behavior and useful diagnostic details are preserved.