feat(backend): Implement Structured JSON Logging in All Node.js Services

[Taleef7]

As a developer or operator, I need application logs to be in a structured JSON format instead of plain text strings. This makes logs machine-readable, allowing for efficient searching, filtering, and analysis in a production logging system (like OpenSearch, Datadog, or Splunk).

Acceptance Criteria:

• A logging library (e.g., pino or Winston) is added to embedding-service, rass-engine-service, and mcp-server.
• All console.log, console.error, etc., statements are replaced with structured logger calls (e.g., logger.info({ ... }), logger.error({ err, ... })).
• Logs should automatically include useful context like a timestamp, log level, and service name.
• When an error is logged, the log entry should include the error message, stack trace, and any relevant request data (like a request ID).