refactor: harden log package for PR#102 review fixes

- Replace bare pointer with atomic.Pointer[slog.Logger] for safe concurrent SetLevel
- Move os.Getenv out of log.go into config.Config (LogFormat, LogLevel, LogSource)
  to satisfy getenv audit invariant
- Add Configure(format, level, addSource) hook wired to cmd/api, worker, migrate
- TTY auto-detect: falls back to human-readable text handler when stdout is a terminal
- Add *Context family (InfoContext, WarnContext, ErrorContext, DebugContext) that
  inject trace_id/span_id when an OTel span is active on the context
- Add otelHandler wrapper on every slog.Handler for native trace correlation
- Harden Mask(): URL credential redaction (user:pass@ → ***@), prefix+suffix truncation,
  clamp prefix 4–20, handle empty/short strings gracefully
- Add 30 test cases covering Mask, level parsing, concurrent SetLevel, JSON/text output,
  env config, and context enrichment (all -race clean)

Author: Luigi

cmd/api/main.go

@@ -52,6 +52,8 @@ func main() {
 	if err := cfg.Validate(config.APIRequiredFields...); err != nil {
 		log.Fatal("config validation failed", "err", err)
 	}
+	addSource := cfg.LogSource == "1" || cfg.LogSource == "true"
+	log.Configure(cfg.LogFormat, cfg.LogLevel, addSource)
 	if cfg.EncryptionKey != "" {
 		if err := pcmicrypto.InitKey(cfg.EncryptionKey); err != nil {
 			log.Fatal("encryption key initialization failed", "err", err)

cmd/migrate/main.go

@@ -20,6 +20,8 @@ import (
 
 func main() {
 	cfg := config.Load()
+	addSource := cfg.LogSource == "1" || cfg.LogSource == "true"
+	log.Configure(cfg.LogFormat, cfg.LogLevel, addSource)
 	if cfg.DatabaseURL == "" {
 		log.Fatal("DATABASE_URL is required")
 	}

cmd/worker/main.go

@@ -38,6 +38,8 @@ func main() {
 	if err := cfg.Validate(config.WorkerRequiredFields...); err != nil {
 		log.Fatal("config validation failed", "err", err)
 	}
+	addSource := cfg.LogSource == "1" || cfg.LogSource == "true"
+	log.Configure(cfg.LogFormat, cfg.LogLevel, addSource)
 	log.Info("config loaded", "db", log.Mask(cfg.DatabaseURL, 40), "redis", cfg.RedisAddr)
 
 	ctxTelemetry := context.Background()

internal/config/config.go

@@ -76,6 +76,11 @@ type Config struct {
 
 	// Dedup (PCMI-011): default ingest dedup mode when tenant/request omit it.
 	DedupMode string
+
+	// Logging
+	LogFormat  string // "json" (default) or "text"
+	LogLevel   string // "info" (default) | "debug" | "warn" | "error"
+	LogSource  string // "1" | "true" to enable source file:line in every record
 }
 
 // APIConfig returns the subset of fields required by the API service.
@@ -135,6 +140,10 @@ func Load() *Config {
 		OTELServiceName:    strings.TrimSpace(os.Getenv("OTEL_SERVICE_NAME")),
 
 		DedupMode: envOr("DEDUP_MODE", "none"),
+
+		LogFormat:  envOr("PCMI_LOG_FORMAT", ""),
+		LogLevel:   envOr("PCMI_LOG_LEVEL", ""),
+		LogSource:  strings.TrimSpace(os.Getenv("PCMI_LOG_SOURCE")),
 	}
 	return cfg
 }