Implement structured logging with pino (P2.17)

Add pino-based logger module for production observability:
- JSON output to stdout for log aggregators (Loki, ELK)
- Configurable via LOG_LEVEL environment variable (defaults to "info")
- Log levels: error, warn, info, debug
- Error objects serialized with type, message, and stack trace
- Child logger support for bound context
- ISO 8601 timestamps in all log entries

Test coverage: 16 tests covering JSON format, log levels, error
serialization, and child loggers.

Total tests now: 553 passing across 31 test files.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -19,6 +19,7 @@
     "lucide-react": "^0.562.0",
     "next": "16.1.1",
     "node-cron": "^4.2.1",
+    "pino": "^10.1.1",
     "pocketbase": "^0.26.5",
     "react": "19.2.3",
     "react-dom": "19.2.3",