Implement inbox read cursors for unread threads

internal/cli/inbox/db.go

@@ -0,0 +1,22 @@
+package inbox
+
+import (
+	"context"
+	"database/sql"
+
+	"ai-workflow-skill/internal/db"
+)
+
+func openInboxDB(ctx context.Context, dbPath string) (*sql.DB, error) {
+	sqlDB, err := db.Open(ctx, dbPath)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := db.ApplyMigrations(ctx, sqlDB); err != nil {
+		_ = sqlDB.Close()
+		return nil, err
+	}
+
+	return sqlDB, nil
+}