Migrate all log.Printf/log.Fatalf to log/slog with structured key-value
attributes per bible go-logging contract.
- Add withRequestID middleware: generates crypto/rand 8-byte hex ID per
request, sets X-Request-ID response header, injects into context
- withErrorLogging uses slog with request_id from context
- writeError internal log calls migrated to slog.Error/slog.Warn
- All handler log calls in api, ingest, history packages use slog
- cmd/reanimator-api configures slog.NewTextHandler(os.Stdout) at startup
- cmd/reanimator-migrate, cmd/reanimator-reset migrated to slog
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
