feat(logging): structured slog logger with JSON/text output (#27)

[Siddhant-K-code]

Closes #27

Summary

Adds pkg/logging — a thin wrapper around stdlib log/slog (Go 1.21+) with no external dependencies.

API

// JSON logger (production default)
logger := logging.New(logging.Config{Level: "info", Format: logging.FormatJSON})

// Text logger for local development
logger := logging.NewDebug()

// Attach request context
logger = logging.WithRequestID(logger, requestID)
logger = logging.WithTraceID(logger, traceID)
logger = logging.WithComponent(logger, "dedup")

Features

• New(Config): configurable level (debug/info/warn/error) and format (json/text)
• NewDefault(): JSON at info level to stderr
• NewDebug(): text at debug level
• WithRequestID / WithTraceID / WithComponent: child loggers with attached attributes
• Unknown level strings default to info

Files

• pkg/logging/logging.go
• pkg/logging/logging_test.go — 11 tests