Scaffold GitManager multi-repo dashboard

Runnable skeleton per AGENT.md: Echo server (/, /help, /healthz, /api/repos), read-only repo scanner with in-memory index, the internal/git boundary, the <repo-list> web component with design tokens, and dev tooling (Dockerfile, docker-compose, air, .env.example).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/logging/logging.go

@@ -0,0 +1,35 @@
+// Package logging builds the application's slog logger. Logs go to stderr
+// (readable console in dev, structured JSON otherwise) and, optionally, to a
+// file. There is no database sink — see AGENT.md §7.
+package logging
+
+import (
+	"io"
+	"log/slog"
+	"os"
+)
+
+// Setup returns a configured *slog.Logger and, if a file sink was opened, an
+// io.Closer to flush/close it on shutdown (nil when no file sink is used).
+func Setup(dev bool, logFile string) (*slog.Logger, io.Closer, error) {
+	var w io.Writer = os.Stderr
+	var closer io.Closer
+
+	if logFile != "" {
+		f, err := os.OpenFile(logFile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
+		if err != nil {
+			return nil, nil, err
+		}
+		w = io.MultiWriter(os.Stderr, f)
+		closer = f
+	}
+
+	var handler slog.Handler
+	if dev {
+		handler = slog.NewTextHandler(w, &slog.HandlerOptions{Level: slog.LevelDebug})
+	} else {
+		handler = slog.NewJSONHandler(w, &slog.HandlerOptions{Level: slog.LevelInfo})
+	}
+
+	return slog.New(handler), closer, nil
+}