feat: Add centralized logging system with @link-stack/logger package

- Create new @link-stack/logger package wrapping Pino for structured logging
- Replace all console.log/error/warn statements across the monorepo
- Configure environment-aware logging (pretty-print in dev, JSON in prod)
- Add automatic redaction of sensitive fields (passwords, tokens, etc.)
- Remove dead commented-out logger file from bridge-worker
- Follow Pino's standard argument order (context object first, message second)
- Support log levels via LOG_LEVEL environment variable
- Export TypeScript types for better IDE support

This provides consistent, structured logging across all applications
and packages, making debugging easier and production logs more parseable.

apps/link/package.json

@@ -19,6 +19,7 @@
     "@link-stack/bridge-common": "*",
     "@link-stack/bridge-ui": "*",
     "@link-stack/leafcutter-ui": "*",
+    "@link-stack/logger": "*",
     "@link-stack/opensearch-common": "*",
     "@link-stack/ui": "*",
     "@mui/icons-material": "^6",