[Refactor]: Migrate stderr logs to structured events

[viiccwen]

Summary

Replace the remaining unstructured stderr diagnostics with sanitized lifecycle events while preserving MCP stdio protocol safety. Remove the now-unused console helper after migrating MCP, webhook, and course catalog logging.

Related Issue

Fixes #114
Follow-up to #91

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Configuration or deployment
• Tests

Changes

• Migrate MCP tool, startup, member notification, and dependency initialization diagnostics to structured events without raw query or platform identifiers.
• Migrate webhook startup/callback failures and course catalog cache/fetch/retry events with consistent component, status, duration, and error-type fields.
• Remove ian.utils.console.eprint and add table-driven privacy, retry-state, callback, and stdio regression tests.

Testing

• Local tests or checks pass
• Manual verification completed
• Not tested; reason:

Commands run:

• make test — 283 passed
• make precommit — all hooks passed
• git diff --check — passed

Impact Checklist

• Discord bot behavior checked, if affected
• MCP server behavior checked, if affected
• Webhook behavior checked, if affected
• Docker or compose changes checked, if affected
• Environment variables documented, if changed
• Logs do not expose secrets or sensitive data

Notes for Reviewers

The MCP regression test verifies that stdio startup emits structured JSON to stderr while leaving stdout empty. Platform integrations are tested with mocked boundaries; no live messages or external requests were sent.